New South Wales Court of Appeal CITATION: WORKERS COMPENSATION (DUST DISEASES) BOARD OF NSW v SMITH, MUNRO AND SEYMOUR [2010] NSWCA 19 HEARING DATE(S): 16, 17 and 19 November 2009 JUDGMENT DATE: 23 February 2010 JUDGMENT OF: Allsop P at 1; Basten JA at 8; Handley AJA at 162 DECISION: (1) Dismiss each of the appeals in respect of the decisions of the District Court. (2) Order that the appellant pay the respondents' costs of the appeals. CATCHWORDS: ADMINISTRATIVE LAW – procedural fairness – adequacy of reasons – factual finding of causation from asbestos in combination with tobacco smoke – whether necessary to attempt to set out arithmetical foundation of finding – whether decision on question of law - APPEAL – civil – statutory appeal – appeal from District Court – appeal against award of the Court in point of law – distinction between point of law, admission of evidence and findings of fact - EVIDENCE – admissibility and relevance – opinion evidence – basis rule – whether basis for opinion identified – whether explicit ruling on objection to evidence necessary - EVIDENCE – weight and sufficiency of evidence – uncontradicted evidence – affidavit evidence of deceased claimants – similarities between affidavits – whether unreliability resulted in unfair prejudice to defendant – Evidence Act 1995 (NSW), s 135 - STATUTORY INTERPRETATION – construction of composite provision – dual limbs – second limb grammatically ambiguous – nature of causal connection envisaged by words "reasonably attributable to" – whether words introduce normative component to determination of statutory entitlement – Workers' Compensation (Dust Diseases) Act 1942 (NSW), s 8(1)(b) - TORTS – negligence – causation – dust diseases – asbestos – tobacco – exposure to both carcinogens – development of lung cancer – whether exposure to asbestos constituted material contribution to carcinoma - WORDS & PHRASES – "asbestosis" – "award of the court in point of law" – "dust disease" – "Helsinki criteria" – "lung cancer" – "material contribution" – "reasonably attributable" – "relative risk" Compensation Court Act 1984 (NSW), s 17 District Court Act 1973 (NSW), s 142J, 142N, 142M Pt 3, Div 8A Evidence Act 1995 (NSW), ss 63, 79, 135 LEGISLATION CITED: Supreme Court Act 1970 (NSW), ss 69, 75A Workers Compensation Act 1926 (NSW), ss 6, 7 Workers' Compensation Act 1987 (NSW), ss 4, 9A, 14 Workers' Compensation (Dust Diseases) Act 1942 (NSW), ss 3, 5, 7, 8, 8I, 9A; Sch 1 Workmen's Compensation (Silicosis) Act 1920 (NSW), s 2 CATEGORY: Principal judgment ACCC v Australian Safeway Stores Pty Ltd [1999] FCA 1269 Australian Broadcasting Tribunal v Bond [1990] HCA 33; 170 CLR 321 Azzopardi v Tasman UEB Industries Ltd [1985] 4 NSWLR 139 Chappel v Hart [1998] HCA 5; 195 CLR 232 Day v SAS Trustee Corporation [2009] NSWCA 222 Dyldam Developments Pty Ltd v Jones [2008] NSWCA 56 Kirk v IRC [2010] HCA 1 March v Stramare (E & MH Pty Ltd) [1991] HCA 12; 171 CLR 506 CASES CITED: Monie v Commonwealth of Australia [2005] NSWCA 25; 63 NSWLR 729 Papakosmas v The Queen [1999] HCA 37; 196 CLR 297 Pettitt v Dunkley [1971] 1 NSWLR 376 Qantas Airways Ltd v Gubbins (1992) 28 NSWLR 26 SAS Trustee Corporation v Pearce [2009] NSWCA 302 Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; 49 NSWLR 262 Soulemezis v Dudley (Holdings) Pty Ltd (1987) 10 NSWLR 247 Stapley v Gypsum Mines Ltd [1953] AC 663 Workers Compensation (Dust Diseases) Board v Veksans (1993) 32 NSWLR 221 Workers' Compensation (Dust Diseases) Board – Appellant PARTIES: Marcia Anne Smith – Respondent (40355/08) Margaret Munro – Respondent (40356/08) Cita Victoria Seymour – Respondent (40357/08) FILE NUMBER(S): CA 2008/290178; 2008/290179; 2008/290167 COUNSEL: G M Watson SC/J Sheller – Appellant P C B Semmler QC/A McSpedden/S Tzouganatos - Respondents SOLICITORS: Goldrick Farrell Mullan – Appellant Turner Freeman - Respondents LOWER COURT JURISDICTION: District Court LOWER COURT FILE NUMBER(S): RJ 2 of 2005; RJ 6 of 2005; RJ 3 of 2005 LOWER COURT JUDICIAL OFFICER: Quirk DCJ LOWER COURT DATE OF DECISION: 14 August 2008 IN THE SUPREME COURT OF NEW SOUTH WALES COURT OF APPEAL CA 2008/290178 CA 2008/290179 CA 2008/290167 ALLSOP P BASTEN JA HANDLEY AJA 23 February 2010 WORKERS COMPENSATION (DUST DISEASES) BOARD OF NSW v SMITH, MUNRO AND SEYMOUR Headnote The husband of each of the respondents was a waterside worker who had died from lung cancer. Each had been a regular and heavy smoker, but had also been exposed to asbestos for varying periods on the waterfront over many years, from the 1950s. Each sought benefits under the Workers' Compensation (Dust Diseases) Act 1942 (NSW) ("Dust Diseases Act"), to which they were entitled if the exposure to the asbestos dust had materially contributed to the lung cancer. In the District Court before Quirk DCJ, expert evidence was adduced as to the epidemiological and statistical basis for determining the probability that exposure to asbestos had materially contributed to lung cancer, as well as expert evidence as to the extent of the exposure that each worker had undergone whilst on the waterfront. Her Honour held that on the basis of the evidence each of the claimants had satisfied the test of causation and accordingly was entitled to statutory benefits. The appellant appealed to this Court from her Honour's decision. The issues for determination on appeal were: (i) whether s 8(1)(b) of the Dust Diseases Act introduces a normative component to a determination of entitlement to statutory benefits; (ii) the availability of a finding that the exposure to asbestos was a material contribution to the lung cancer; (iii) whether her Honour erred in treating as a legal test, certain expert evidence as to the determination of the statistical likelihood of causation; (iv) whether her Honour erred in admitting certain expert evidence as to each workers' exposure to asbestos in the absence of a sound basis for that evidence; (v) whether her Honour erred in admitting portions of the deceased workers' affidavits despite there allegedly being contradictory evidence, and the affidavits of two of the workers being strikingly similar; (vi) whether her Honour's reasons were inadequate, and (vii) the relevance of her Honour's delay in delivering judgment. The Court held, dismissing the appeal: In relation to (i) (per Basten JA, Allsop P and Handley AJA agreeing) 1. Section 8(1)(b) contains two limbs. Rather than introducing a normative element, the use of the phrase "reasonably attributable" in the second limb requires a causal connection between the occupation and the relevant exposure, in contrast to the first limb, which requires a causal connection between the relevant disease and death. Neither the legislative history of the Dust Diseases Act nor its statutory context within the wider workers' compensation scheme indicates that a normative assessment of the workers' conduct is relevant: [31], [42]–[46]. In relation to (ii) (per Basten JA, Allsop P and Handley AJA agreeing) 2. The preponderance of expert evidence indicated that an assessment of the statistical likelihood of exposure to asbestos having materially contributed to the lung cancer needed to take into account the synergistic effect of exposure to both tobacco smoke and asbestos, by which each carcinogen interacted with the other so as to increase the overall likelihood of contracting lung cancer: [60]–[61], [66]–[68]. 3. One factor can contribute to an outcome even though, relative to another factor, it has a minor effect. All that is required is that the effect be "material". Any assessment of this materiality is an evaluative judgment, and it was open upon the evidence for her Honour to conclude that the exposure to asbestos was such a material factor: [72]. 4. An ultimate finding of causation may be based on a number of inferences drawn from primary facts, which may cumulatively allow the ultimate finding to be made. It depends on the circumstances as to whether these inferences are available through the application of logic and commonsense, technical inquiry, or expert assessment. In circumstances where epidemiological studies cannot provide scientific certainty as to the probability of a material contribution, and further uncertainty surrounds the precise experience undergone by the individual to whom the probability relates, a logically reasoned inference of material contribution based upon the available expert evidence betrays no error: [124]–[134]. Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; 49 NSWLR 262, considered. Australian Broadcasting Tribunal v Bond [1990] HCA 33; 170 CLR 321; March v Stramare (E & MH Pty Ltd) [1991] HCA 12; 171 CLR 506; Chappel v Hart [1998] HCA 5; 195 CLR 232; Azzopardi v Tasman UEB Industries Ltd [1985] 4 NSWLR 139 at 156, referred to. In relation to (iii) (per Basten JA, Allsop P and Handley AJA agreeing) 5. The relevance of the Helsinki Criteria derived from its nature as a statement of collective expert opinion as to when exposure to asbestos, in isolation, would more likely than not have caused the contraction of lung cancer, rather than as a legal test. Her Honour demonstrated no error in treating it as such: [77]–[78]. In relation to (iv) (per Basten JA, Allsop P and Handley AJA agreeing) 6. The basis for the expert evidence as to the accumulated exposure experienced by each worker was both identified, and available for exploration in cross-examination. Once that basis had been identified and accepted by her Honour, the evidence was admissible and no further reasons were necessary: [91]–[99], [101]. In relation to (v) (per Basten JA, Allsop P and Handley AJA agreeing) 7. There is a difficulty in assessing the reliability of evidence where contrary material cannot be put to a witness in cross-examination. However there was nothing inherently prejudicial about the evidence, it was relevant to a critical issue in the case, and it remained capable of subversion by contrary evidence: [106]. Dyldam Developments Pty Ltd v Jones [2008] NSWCA 56, cited. Papakosmas v The Queen [1999] HCA 37; 196 CLR 297; ACCC v Australian Safeway Stores Pty Ltd [1999] FCA 1269, referred to. 8. Where similarities between two affidavits are explicable, any prejudice caused by admission of the evidence must be assessed in relation to its probative value. Her Honour's conclusion that any significance that could be attached to those similarities, such as unreliability, did not outweigh the probative value of the affidavits, was not shown to be erroneous: [108]–[112]. In relation to (vi) (per Basten JA, Allsop P and Handley AJA not deciding) 9. Although there is a legal obligation to give adequate reasons, in circumstances where the statutory obligation of the trial court was to determine the matter on "the real merits and justice of the case", it is inappropriate for an appellate court to conduct a critique of the written reasons, not to search for error otherwise revealed, but to address an amorphous standard of "adequacy":[138] – [139]. Soulemezis v Dudley (Holdings) Pty Ltd (1987) 10 NSWLR 247; Pettitt v Dunkley [1971] 1 NSWLR 376; Day v SAS Trustee Corporation [2009] NSWCA 222; Day v SAS Trustee Corporation [2009] NSWCA 222, referred to. (per Basten JA, Allsop P and Handley AJA agreeing) 10. The basis of her Honour's conclusion upon the synergistic effect of exposure to both tobacco smoke and asbestos required no greater elucidation than that provided: [142] – [143]. In relation to (vii) (per Basten JA, Allsop P and Handley AJA agreeing) 11. Delay in delivering judgment may in some cases lead an appeal court to be reticent in accepting the benefits commonly attributed to the trial judge in assessing the evidence where the assessment has been long delayed. However in circumstances where no challenge to factual findings is permitted, no inference of error can be drawn from such a delay: [154]. Monie v Commonwealth of Australia [2005] NSWCA 25; 63 NSWLR 729, distinguished. IN THE SUPREME COURT OF NEW SOUTH WALES COURT OF APPEAL CA 2008/290178 CA 2008/290179 CA 2008/290167 ALLSOP P BASTEN JA HANDLEY AJA 23 February 2010 WORKERS COMPENSATION (DUST DISEASES) BOARD OF NSW v SMITH, MUNRO AND SEYMOUR Judgment 1 ALLSOP P: I have had the advantage of reading the reasons of Basten JA. I agree with the orders proposed by him and, subject to one reservation, with his Honour's reasons. 2 I would reserve for another occasion any analysis of the consequence for legal review under the District Court Act 1973 (NSW), s 142N of inadequate reasons. 3 Further, it is also necessary to say something as to how the appeal was propounded. In doing so I am not intending personal criticism of counsel; nevertheless, the issue needs to be broached because of its importance. The notice of appeal did not provide the Court, the respondents or the respondents' legal advisers with any clear understanding of the alleged errors of law by the primary judge which fell within s 142N. 4 Notices of appeal should inform the respondent of the substance of the appellant's case on appeal with economy, clarity and precision. That written submissions will be required does not lessen this requirement. 5 The statutory bases for appeal to the Supreme Court or the Court of Appeal are variously worded. The Court of Appeal's webpage (http://www.lawlink.nsw.gov.au/lawlink/Supreme_Court/ll_sc.nsf/pages/SCO_ca) can assist practitioners and litigants with its comprehensive statement of the relevant Acts and cases ("NSW Statutory Appeals and Referrals on Questions of Law"). The Supreme Court Act 1970 (NSW), s 69 and the importance of jurisdictional error: Kirk v IRC [2010] HCA 1 may also need to be considered in particular cases. 6 All too often in the Court's experience, notices of appeal and written submissions on behalf of appellants fail to address the nature of the "appeal" rights that have been invoked. Failure to do so can affect the interests of the appellant as well as impeding the efficient disposition of the appeal. 7 The notice of appeal is a vital tool for litigants and the Court in the efficient and economical despatch of appeals. Its importance should be recognised by practitioners in the observance rather than in the breach of the relevant rules. 8 BASTEN JA: INDEX Paragraph Number Nature of appeal 11 Issues on appeal 15 Statutory scheme for compensation: construction of s 8 28 Causal connection: expert evidence 48 Her Honour's reasoning with respect to relative risk 66 Admission of evidence: Helsinki criteria 73 Admission of evidence: Evidence Act, s 135 81 Admission of evidence: Dr Francis' report 85 Admission of evidence: affidavits of workers 102 Ground 2: challenges to factual findings 113 Ground 2: inadequacy of reasons 135 Ground 2: Mr Smith – asbestosis 144 Ground 3: Delay in delivering judgment 151 Conclusions 156 9 Each of the three respondents to the appeal is a widow whose husband died of lung cancer. Each of the men was a regular and heavy smoker, but each was also exposed to asbestos dust whilst working on the waterfront for varying periods over many years, from the early 1950s. In each case, the critical question identified by Quirk DCJ sitting in the "residual jurisdiction" of the District Court was whether exposure to asbestos dust materially contributed to the lung cancer. If it did, each of the workers (and now their widows) was (and is) entitled to benefits under the Workers' Compensation (Dust Diseases) Act 1942 (NSW) ("the Dust Diseases Act"). It was from her Honour's conclusion that the claimants had satisfied that requirement that the present appeals were brought. 10 The issue is one of causation in circumstances where medical science is unable to identify, in the case of any particular person suffering from lung cancer, the precise cause of the disease. According to the appellant, although both smoking and asbestos were capable of causing lung cancer, the statistical likelihood in each case that asbestos caused the disease was less than 50%. Accordingly, the appellant argued, the Tribunal had been in error in finding that each respondent had made good, on the balance of probabilities, a causal connection between exposure to asbestos and the lung cancer suffered by each of the deceased respectively. Nature of appeal 11 The Dust Diseases Act creates a Board, known as the Workers' Compensation (Dust Diseases) Board, to which a claimant may apply for payment of compensation, such compensation being payable in circumstances to which it will be necessary to refer in more detail, but may be broadly described as circumstances in which a worker was disabled (or had died) from a "dust disease" contracted as a result of occupational exposure to inhalation of dust. Entitlement to an award of compensation from the Board is contingent upon a "medical authority", constituted under s 7 of the Dust Diseases Act, certifying the existence of the necessary causal connection between the exposure and the disability (or death): s 8(1). Where a claim is rejected by the medical authority declining to certify the necessary elements, a person dissatisfied with the decision may appeal to the District Court: s 8I. That Court determines the "appeal" on the merits in exercise of its residual jurisdiction: District Court Act 1973 (NSW), Pt 3, Div 8A. 12 It was common ground that the District Court was required to consider the matter afresh and reach its own conclusion on the evidence before it, as held by this Court in Workers' Compensation (Dust Diseases) Board v Veksans (1993) 32 NSWLR 221 at 230D (Kirby P) and at 238C and F (Handley JA, Sheller JA agreeing). So much followed from the obligation to decide the case "on the real merits and justice of the case": s 142J. (Curiously, there was no reference in Veksans to the predecessor of s 142J, namely s 17 of the Compensation Court Act 1984 (NSW).) 13 The appeal to this Court from the judgment in the District Court is brought by a party aggrieved "by an award of the [District] Court in point of law or on a question as to the admission or rejection of evidence": District Court Act, s 142N(1). 14 In the Dust Diseases Act, the term "award" is used synonymously with a final order or judgment under which compensation is payable: see, eg, s 8(1), referring to the circumstances in which a person is "entitled to an award from the Board, and to receive compensation at the prescribed rates from the Fund". However, it seems unlikely that the term "award" was intended in some restrictive sense in the District Court Act, the appeal to that Court being one which may be brought from, as in this case, a decision of the medical authority, which is only a step in the course of obtaining an award from the Board. That the term "award" has a wide meaning in s 142N is confirmed by s 142M which states that in the subsequent section, "award includes interim award, order, decision, determination, ruling and direction": s 142M(1). There may be a question as to whether s 142N requires the identification of a decision of the District Court on a point of law (or on a question of admissibility of evidence) or whether it is sufficient if the final conclusion of the Court is affected by an error of law. Before considering that issue, it is convenient to identify the grounds of appeal relied upon by the appellant Board. Issues on appeal 15 Although, in its written submissions, the appellant sought to distinguish between the cases involving each of the three workers, the notices of appeal were identical. They provided no element of particularity. 16 The written submissions for the appellant must apparently be analysed by the Court in order to determine the grounds. Despite the inappropriateness of this course, pointed out to counsel for the appellant during the course of the hearing of the appeal, no application was made to amend the notice of appeal. The written submissions themselves (and indeed the oral submissions) were less than meticulous in distinguishing between: (a) something which might be described as an "award of the Court in point of law"; (b) a question as to the admission of evidence, and (c) a review of the decision of the Court on the merits. This Court was left with the impression that these boundaries were deliberately blurred in the presentation of the case. It causes great difficulty for the Court in being sure that it has resolved all the issues which were legitimately able to be raised on the appeal. This unsatisfactory state of affairs has resulted from the conduct of the appeal by the appellant Board, a statutory authority the members of which are appointed by the Minister: Dust Diseases Act , s 5(1). The respondents to the appeal, whose interests are entitled to be taken into account in identifying the proper course to be taken in the proceedings, are the widows of workers who may have claims, not to some largesse dispensed by the Board, but to the statutory entitlements created by the Act and administered by the Board. 17 In each case ground 1 alleged error in the construction of s 8 of the Dust Diseases Act. Precisely how the trial judge was said to have erred will be considered below, but the application of s 8(1)(b) was a factor addressed by her Honour and identifiable error in that respect will fall within the legitimate scope of the present appeals. 18 The second ground of appeal involved a number of limbs, with differing legal significance. The ground read as follows: "2. The Trial Judge erred in law in making, or purporting to make, findings: (a) in the absence of evidence to support the finding; (b) in the absence of providing adequate reasons for making the findings; (c) in making findings in the context of the application of an incorrect legal test; (d) on the basis of evidence wrongfully admitted; (e) wrongly relying upon expert evidence." 19 Perhaps curiously, given the formulation of this ground, the principal submission was that her Honour had failed to make particular findings, namely findings in each case of the effect of heavy smoking over extended periods. The respondents did not complain as to this approach, no doubt because it was understood to be a different way of expressing the primary complaint, namely that it was not open to her Honour to infer, on the evidence properly before her, that exposure to asbestos dust materially contributed to the lung cancer from which each of the workers died: ground 2(a). However s 142N(1) is construed, a ground complaining that there was no evidence to support an ultimate finding may fall within the scope of the statutory appeal if it could be said that her Honour determined, whether expressly or by implication, that no evidence was needed of a particular fact, or that evidence which did not in truth bear upon the fact was available to support it. 20 Grounds 2(c) and (d) (although not particularised) potentially fell within the scope of an appeal under s 142N. Ground 2(b), concerning the adequacy of the reasons of the trial judge, may be problematic, but the jurisprudential problems are not critical because the substance of the ground is not made out, as will be explained below. Paragraph 2(e) may or may not have involved a decision by the trial judge in point of law: it was not separately addressed in the course of argument and may be put to one side. 21 The third ground of appeal alleged that error could be "inferred" from the delay between the hearing of the case in the District Court and the delivery of judgment (a period of 18 months). The relevance of delay in an appeal of this kind will need further consideration when her Honour's reasons have been considered in detail. 22 Apart from the constraints imposed on the appellant by the limited nature of the appeal (there having been no attempt to rely upon judicial review powers of the Court pursuant to s 69 of the Supreme Court Act 1970 (NSW)), the core of the appellant's case turned on the availability of inferences in relation to the question of causation. In each case the premise was that the lung cancer should have been attributed to the physical insult to the workers' lungs from one of two carcinogens, namely tobacco smoke and asbestos dust. The appellant contended that the likelihood of the lung cancer having resulted from smoking was many times that of exposure to asbestos dust and, accordingly, none of the respondents could demonstrate that, on the balance of probabilities, the cancers resulted from exposure to asbestos dust. Thus, for example, if epidemiological studies demonstrated that in particular circumstances the likelihood of a cancer being attributable to exposure to asbestos dust was 20%, as compared with 80% in respect of smoking, the worker would fail to establish a probable causal connection between the disease and exposure to asbestos dust. 23 The alternative approach, adopted by the respondents, was that with exposure to both tobacco smoke and asbestos dust, it was reasonably likely that the two agents had interacted (the synergistic effect), with the result that each probably contributed to the disease in a material respect in a particular individual. Although it might be possible statistically to separate the likely contributions of each agent, that was neither necessary nor appropriate for determining a disease was due to a particular agent, in the relevant statutory context. 24 The appellant accepted that the concept of material contribution reflected at least part of the test to be applied in determining the eligibility for an entitlement under the Act. It also appears to have been assumed that the claimants needed to establish the causal connection according to the civil standard, on the balance of probabilities. This approach involved two assumptions. The first was that the claimant bore a burden of proof and the second the standard to which the court needed to be satisfied for the claimant to succeed. 25 The first assumption is doubtful. Although the appeal is said to be "against" the decision of the Board, and the Board is a "necessary party to an appeal", it does not follow that the claimant bore any legal burden. Further, no account appears to have been taken of the statutory obligation of the Court, in the exercise of its residual jurisdiction, to determine the matter "on the real merits and justice of the case", the Court not being bound "to follow strict legal precedent": District Court Act, s 142J(1). The precise operation of such provisions is obscure, particularly in circumstances where an appeal lies from a decision of the Court in point of law and from the rejection or admission of evidence: cf Qantas Airways Ltd v Gubbins (1992) 28 NSWLR 26. Nevertheless, it might well have been arguable that the claimants did not bear a legal burden of proof and that the Court did not need to be satisfied on the balance of probabilities. However, given the approach adopted at trial, it is appropriate that this Court proceed on the basis that the civil standard did apply and that the respondents bore a burden of proof. 26 It is also an open question as to whether the Board acted properly in treating the proceedings in the District Court (and in this Court) as strictly adversarial and as requiring or at least permitting it to challenge the admissibility of evidence and cross-examine extensively witnesses called by the present respondents. The Board remains a decision-making authority in relation to their entitlements, in circumstances where its conduct may have caused the claimants (or the Legal Aid Commission) to amass large liabilities for legal costs as a result of the manner in which the Board conducted the litigation: cf The Queen v Australian Broadcasting Tribunal; Ex parte Hardiman [1980] HCA 13; 144 CLR 13 at 35-36; Oshlack v Richmond River Council [1998] HCA 11; 193 CLR 72 at [12] (Gaudron and Gummow JJ). 27 It is not necessary for present purposes to consider the correct approach to be undertaken by the medical authority in determining such matters. Each of the respondents was unsuccessful before the authority, but exercised the right of appeal granted by s 8I of the Dust Diseases Act. This Court has expressed the view that the District Court, in exercising original judicial jurisdiction, is required to give weight to the expert opinion of the authority: Veksans at 241B. No such issue was raised in the present case and it may be difficult to know what weight should be given to a decision of the authority, which is not accompanied by reasons and which may be determined on the basis of material (and the experience of the members of the authority) which differ from the evidence properly before the District Court. In any event, nothing turned on that matter in the present case and it was accepted that the District Court was bound to determine the case in accordance with the material properly before it under the Evidence Act 1995 (NSW). Statutory scheme for compensation: construction of s 8 28 The Dust Diseases Act prescribes the circumstances in which a person shall be entitled to an award from the Board and to receive compensation at prescribed rates: s 8(1). Paragraphs (a) and (b) deal separately with a person suffering a disability and a person who has died from a dust disease. In each case the "medical authority", constituted under s 7, is required to certify certain things, including that the disability for work or the death is "from a dust disease". In the present case, the relevant dust disease was "asbestos induced carcinoma": s 3 and Schedule 1. 29 That which the medical authority was required to certify in the case of s 8(1)(b) involved a number of elements, differently expressed, identified as preconditions to entitlement to compensation in the following terms: "(b) where the medical authority certifies that a person died from a dust disease and that the person's death was reasonably attributable to the person's exposure to the inhalation of dust in an occupation to the nature of which the disease was due ….: 30 In this case, the disease in question, to qualify as a "dust disease", itself involved a causal element, namely that the cancer must be "asbestos induced". 31 It is clear that s 8(1)(b) has two limbs, the first requiring a casual connection between the death and a dust disease. The structure of the second limb is grammatically unclear. The question of law raised in the present case concerned the meaning of the words "reasonably attributable to". They envisage a connection between two factors or events, so that the first step must be to identify those two factors or events. The last nine words of the second limb identify something to which the disease was due, or more precisely, to the nature of which the disease was due. Although the words follows "an occupation" it would be awkward, given the context, to describe the disease as due to the nature of an occupation. The other relevant nouns are "exposure", "inhalation" and "dust". The ordinary meaning of that language would suggest that it was the inhalation of dust to which the disease was due but the addition of the words "the nature of" make it more likely that the factor being characterised is either the exposure or the dust. It is more likely that it refers to the exposure, as the primary purpose of the second limb appears to be to address the circumstances of the exposure, namely that it must occur "in an occupation". Domestic or recreational exposure would not do. Where the exposure may have arisen in more than situation, it is the occupational exposure (or the nature thereof) to which the disease must reasonably be attributable, in order to satisfy the second limb. 32 The legal error asserted by the appellant in respect of the construction of s 8 involved the identification of the two limbs of the provision, which her Honour was said to have elided. The first was said to involve a causal connection, or in the terms of the written submissions, "a pure question of causation". The second limb was said to involve "an additional requirement" involving a "normative component". 33 In respect of the first question, the appellant submitted that a claimant under the Dust Diseases Act must prove that asbestos "materially contributed to the contraction of the lung cancer". Although that language is taken from case-law identifying principles of causation in negligence, that approach was not disputed and the submission should be accepted. Error was asserted based on the proposition that as smoking was the predominant cause of lung cancer, it could not be said that exposure to asbestos dust did more than increase the risk of lung cancer. 34 The appellant purported to identify three reasons why, in addressing the second limb, her Honour had erred in concluding that each of the deaths in question was "reasonably attributable" to exposure to the inhalation of asbestos dust. The first was no more than a repetition of the proposition that smoking is the overwhelming cause of lung cancer. There was no suggestion that this basis of complaint involved her Honour's rejection of some additional "normative" element. 35 The second reason was that each of the workers acted "unreasonably" in smoking or continuing to smoke when the dangers associated with that conduct were well known: written submissions, par 37. That was identified as a submission made by the appellant to the trial judge explaining that the respondents could not show reasonable attributability: appeal submissions, par 36. At the hearing of the appeal, the appellant withdrew that statement: Tcpt, 19/11/09, pp 17-18. What was meant by that withdrawal was unclear; it seems unlikely that the appellant did not know what submission it had made to the trial judge. However, the purpose of withdrawing the submission was apparently so that the appellant could now assert that her Honour was in error in suggesting that the appellant had indeed put the argument below in precisely the way identified in par 37 of the submissions on appeal: Tcpt, CA 16/11/09, p 37 (20). Although counsel promised to "come back to" that alleged error, he did not. What he did do was refer to evidence of two experts which was supposedly "evidence on unreasonableness of smoking", which was "not considered": document handed up on appeal, item 10. 36 No error was demonstrated in the passage in the judgment below where her Honour rejected the concept of "unreasonable conduct" and nothing was left upon which any "normative component" could have been based. The submission that her Honour's rejection of the argument occurred "without giving reasons or referring to the evidence" was inapt and tendentious. Her Honour treated the submission as raising a question of construction which was addressed and rejected. 37 The construction point was not elucidated in oral argument. The statement of the trial judge that "the defendants' submission that continuing to smoke by the deceased workers constituted 'unreasonable conduct' which leads to the legal conclusion that disability and death were not 'reasonably attributable' to asbestos exposure", was disowned as "not the way in which the submission was framed: Tcpt, 16/11/09, p 37 (20). The Court was not assisted by reference to how the submission had in fact been framed, although the appellant accepted (written submissions par 37) that the application of the "reasonably attributable test" which had been proposed below was "that by smoking, especially by smoking so heavily, the workers were acting unreasonably". The complaint that her Honour misconceived the submission was not made good. 38 The third matter relied upon as a reason why her Honour erred in her construction of the phrase "reasonably attributable" was said to be "that each of the workers continued to smoke for long after their exposure to asbestos ceased". However, this appears to be a reiteration, in different form, of the complaint that her Honour failed to take account of the history of smoking of each of the workers. It does not attempt to identify a point of construction in relation to s 8(1)(b). 39 The phrase "reasonably attributable" involves a causal element, but in this instance the connection is between the occupation and the relevant exposure or inhalation, rather than between the disease and death. Beyond this, it is not necessary to go for present purposes. The only relevant exposure to asbestos dust was occupational, arising in the course of stevedoring activities undertaken by the workers. 40 Her Honour clearly understood the submission as to the relevance of the phrase "reasonably attributable" as an attempt to impose a more restrictive test of causation than that of material contribution. Her Honour stated at [18]: "The question at issue therefore, in each case is whether the carcinoma from which each worker died was reasonably attributable to the person's exposure to the inhalation of [Asbestos] dust or asbestos induced . In either formulation the test is satisfied if asbestos dust materially contributed to the carcinomas from which the workers died." 41 This statement of the issues, which incorporated the relevant definition of a dust disease was sufficient for her Honour's purposes. No reference was made to the question of occupation, except inferentially by reference to "the workers". That did not reveal error in any event, because that aspect of the test was not in issue. 42 The correctness of this approach is confirmed by reference to the Dust Diseases Act in its original form, in which questions of disablement and death were dealt with in a single formula requiring the medical authority to certify that: "(a) the worker's disablement for work, or (b) the worker's death, from the disease was reasonably attributable to his exposure to the inhalation of silica dust in New South Wales in an employment to the nature of which the disease was due …." 43 At that time the Dust Diseases Act, known as the Workers' Compensation (Silicosis) Act 1942 (NSW) ("the 1942 Silicosis Act"), added an additional restriction, namely that the inhalation must occur in New South Wales, referred to employment rather than occupation and, as in the present formulation, permitted consideration of the nature of the employment, rather than a measurable exposure to what was then limited to silica dust. Further, at that time there was no appeal from a determination of the medical authority, so that the language of the section was required to be applied by medical practitioners and not lawyers or judges. There is nothing in the language which suggests some causal or normative requirement of a kind more restrictive than material contribution. 44 The 1942 Silicosis Act had been preceded by the Workmen's Compensation (Silicosis) Act 1920 (NSW). That Act had empowered the Minister to establish a scheme for payment of compensation by the employers of workmen in industries "involving exposure to silica or other dust": s 2(1). Entitlement to a benefit depended upon either death or total disablement, or suffering from silicosis to such a degree as to make it dangerous for them to continue to work in the industry. In the first category, the primary basis of entitlement was that the worker had "suffered death or total disablement" from the disease known as silicosis and, in the latter, that he was found on medical examination "to be suffering from silicosis". The legislation assumed that silicosis was caused by exposure to silica. However, in each case, entitlement could also arise where the person suffered from any other disease of the lungs "caused by exposure to silica or other dust". 45 This legislative history reveals that the various concepts of death or disablement, disease, exposure to dust, in an occupation, were all present, but that uniformity of terminology suggesting causal connection, was never a feature of the legislative scheme. 46 The intention that the introduction of the phrase "reasonably attributable" gave rise to some normative element is implausible. Since 1920, the legislative scheme for compensation for dust diseases has been treated as part of the general workers' compensation scheme, with which the legislation is required to be construed. That scheme has at all times required a causal connection between the injury or disease and employment but has never depended upon any element of fault on the part of the employer: see, eg, Workers Compensation Act 1926 (NSW) ("the 1926 Act"), s 6(1); Workers' Compensation Act 1987 (NSW), s 4. It was not until 1996 that a requirement that the employment must be "a substantial contributing factor to" the injury was inserted in the current legislation: s 9A. The exclusion, in cases involving psychological injury of certain forms of "reasonable action" of the employer was introduced in 1995, but does not extend to other than psychological injury. The legislation has, throughout the relevant period, excluded compensation for injury "solely attributable to the serious and wilful misconduct of the worker" and in the case of an "intentional self-inflicted injury": see the 1926 Act, s 7(2) and (3) and the current Act, s 14(2) and (3). 47 No reliance was placed, in the course of the appeal, on the requirement that the Dust Diseases Act "shall be construed with the Workers Compensation Act 1987", nor was any reference made to the provisions of s 14 of the latter Act. Nor was it suggested that continued smoking constituted serious and wilful misconduct or an intentional self-inflicted injury: any such suggestion would have raised a factual issue for determination by the trial judge. Accordingly, accepting that the phrase "reasonably attributable" may allow for circumstances where, despite the existence of a dust disease, compensation is not payable, the possible factual basis, absence of occupational exposure, was absent in the present cases. Accordingly, the appellant's complaint of legal error in the construction of s 8(1) must fail. Causal connection: expert evidence 48 At the heart of the appeal lay the proposition that in each case the respondents had failed to demonstrate that the death of each of the workers had been caused by exposure to asbestos dust. The appellant asserted that it was undeniable that in each case the cause of the lung cancer, and hence death, was exposure to tobacco smoke. The trial judge, the submission continued, failed to advert to that central argument. 49 To assess this complaint more fully, it is necessary to identify briefly the context in which the complaint arose. In one sense, the underlying factual premises were not in dispute. Thus, each of the workers had died of lung cancer, each having smoked cigarettes for considerable periods and in considerable numbers. Further, it was common ground that medical science could not identify in an individual case the actual cause of lung cancer. These facts, the appellant correctly contended, posed significant hurdles for each of the respondents in seeking to establish an entitlement to compensation. 50 The appellant recognised, and indeed insisted, that the question of causation could only be addressed through epidemiological studies which identified the likelihood of lung cancer being caused by one or another pathogen. These studies, upon which all parties relied, demonstrated, according to the appellant, that the likelihood of any particular lung cancer being caused by asbestos, even in cases of known exposure to asbestos dust, was minimal compared with the likelihood of the cancer being caused by smoking. The approach adopted by the experts was that summarised by Professor Geoffrey Berry and extracted by her Honour at [109]. Professor Berry wrote (in a report concerning the late Mr Barry Smith): "It is impossible to state the cause of a condition, such as lung cancer, in an individual with certainty. This is because there are a variety of possible causes, and also cases for which no particular cause is known. For example cases occur in life-long non-smokers who have not been exposed to dusts or fibres; these cases are sometimes referred to as background cases. However, from epidemiological studies that have been conducted on groups of people, and analysed using statistical methods, it is possible to obtain information on the risk of exposures to various agents. Risk is usually expressed in terms of the measure relative risk (RR) . This is defined as The ratio of the Risk of disease or death among the exposed to the risk among the unexposed . As an example it has been estimated that the relative risk in smokers compared with non-smokers is 15. Another example is that the relative risk of lung cancer due to asbestos exposure in a particular factory in London was estimated at 3. These are both average values and further analysis shows that the relative risk due to smoking depends on the amount smoked, and that due to asbestos exposure on the extent and intensity of that exposure. That is, for an agent that increases the cancer risk, higher exposures increase the risk more than low exposures. Another measure used is attributable fraction among the exposed . This is defined as (RR minus 1)/RR, so that a relative risk of 15 gives an attributable fraction of 14/15 = 0.93 or 93%. An interpretation of this figure is that 93% of the lung cancers in smokers are attributable to smoking (and 7% are background cases). Note that a relative risk of 1 indicates no excess risk, so that a relative risk of 15 may be divided into 1 (background) and 14 (excess). Thus, for an individual smoker who develops lung cancer, although it is not certain that the lung cancer was caused by smoking, one can say that the probability that it was due to smoking is 93%. A relative risk of 2 gives an attributable fraction of 50%. That is, it is equally likely that the condition was due to the exposure or not. For relative risks higher than 2 then the exposure is the more likely cause, and for a relative risk less than 2 the exposure is the less likely cause." 51 There is an attractive simplicity in the statistical proposition that only a relative risk in excess of 2 indicates that it is more probable than not that the particular exposure being measured was the cause of the disease. There is also an attractive simplicity in the appellant's contention that, in the example given by Dr Berry, where the relative risk resulting from smoking is five times that created by asbestos exposure, a person who has been subject to both cannot possibly contend on the balance of probabilities that his lung cancer was due to asbestos exposure, it being five times more likely that it was due to smoking. 52 There are, however, a number of confounding factors which diminish or dissipate those considerations. The first is the fact that relative risk will, in any particular case, depend upon the duration and intensity of exposure, both in the case of asbestos dust and tobacco smoke. In relation to smoking, the large number of known cases appears to have allowed for a degree of precision and relatively high confidence levels in the calculations of relative risk, dependent upon the number of cigarettes smoked per day, the period over which the smoking continued, but subject to significant reduction after cessation. 53 Errors in estimation are of particular significance in the case of a deceased worker whose smoking habits over a lifetime must be reconstructed from information obtained from others. Even greater difficulties arise with respect to asbestos exposure. Professor Douglas Henderson, who was called by the respondents, was a co-author of a document commonly known as "The Helsinki Criteria" which sought to establish a standard for the intensity of exposure to asbestos dust that would give rise to a relative risk of 2. The figure arrived at was a cumulative exposure amounting to 25 fibres/ml–years, being a calculation which included both the intensity and duration of exposure. However, the Helsinki Criteria themselves noted that "the relative risk of lung cancer is estimated to increase .5% to 4% for each fibre per cubic centimetre per year (fibre-years) of cumulative exposure. With the use of the upper boundary of this range, a cumulative exposure of 25 fibre-years is estimated to increase the risk of lung cancer two-fold. Clinical cases of asbestosis may occur at comparable cumulative exposures." 54 The identified range involved a factor of eight between its minimum and maximum limits, suggesting that at the lower boundary of the range, the relative cumulative exposure may be 200 fibre-years. The disparity depends primarily on the nature of the asbestos; thus, as explained by Dr Berry: "Based on a published analysis of exposure–response relationships, a cumulative exposure of 25 fibre-years is a reasonable figure to use for a doubling of risk for exposure that is predominantly to amphibole (crocidolite and amosite) asbestos, whilst the other end of the range (doubling of risk at 200 fibres/ml years) may be appropriate for exposure to commercial chrysotile other than in textile production. 55 Accordingly, estimates of relative risk in relation to asbestos exposure depend not only upon measurements of the amount of dust in the environment from time to time, but also on the type of asbestos involved. The reference at the end of Dr Berry's comment to textile production alluded to a study of textile workers in the USA in which surprisingly high levels of asbestos-related lung cancer were detected, suggesting the circumstances of the exposure also had a bearing on the outcome. 56 The reference to asbestosis in the last sentence quoted above from the Helsinki Criteria should also be noted. There are experts who support (or have supported) the proposition that a finding of asbestosis is a precondition to a finding of asbestos-induced lung cancer (known as the precursor theory). That did not receive substantial support amongst the experts who gave evidence in the present case, and was not accepted by her Honour. However, the Helsinki Criteria suggest that the existence of asbestosis, though not a precondition to a finding of probable causation, may indicate a level of exposure to asbestos consistent with that giving rise to a two-fold increase in the risk of lung cancer. 57 Evidence of the intensity of exposure suffered by the three deceased workers in the present case was obtained from industrial hygienists, who provided evidence to the Court. The respondents' witness in that respect was Dr Eva Francis, who had investigated asbestos workplaces in New South Wales as an officer in the Health Department of New South Wales from early 1971. Dr Francis had personal experience in investigating conditions on the Sydney waterfront. Dr Geoffrey Pickford, called by the appellant, was an occupational hygienist who had lengthy experience with industrial users of asbestos from 1977 until 1988, when he became a private consultant, but had not himself carried out testing on the waterfront or in the holds of ships. 58 The trial judge said she accepted Dr Francis' estimates as being "more likely to reflect the probable exposure of the three deceased workers than Dr Pickford's, although she may have overestimated the exposure to some extent": at [165]. 59 However, her Honour also appears to have accepted the evidence of Professor Henderson that the estimates of exposure provided by the occupational hygienists were both "subject to substantial imprecision, being retrospective estimates of exposures that occurred 20 or 30 years ago": Tcpt, 08/02/07, p 145 (35). Accordingly, Professor Henderson preferred to base his assessment on other factors including the work histories of the individuals and his own experience of cases of asbestosis among workers in similar situations. As her Honour noted at [92] Professor Henderson had expressed doubts in his evidence as to the scientific rigour of measurements taken by occupational hygienists, "taking into account the widely disparate estimates that I see": Tcpt, 08/02/07, p 143 (5). Professor Henderson, who was a specialist pathologist with extensive clinical experience with asbestos workers, considered it appropriate to take into account the kinds of cases of undoubted asbestos-induced disease which had arisen amongst waterside workers whose work experience was similar to that of the deceased claimants. 60 Quite independently of the difficulties in being sure of the actual exposure of individuals to asbestos dust, the great majority of the experts who expressed opinions in the present case accepted that smoking and asbestos exposure had an interactive or synergistic effect. As Professor Henderson explained (Tcpt, 08/02/07, p 110 (20)): "I think most studies accept that there is a synergistic interactive effect between tobacco smoke and lung cancer [sic] so that the combined effect is greater than the sum of the individual effects. … The example sometimes used is that of United States insulation workers where from their asbestos exposure if they are non-smokers, they have a risk of about five. If they are smokers and not exposed to asbestos, then they have a risk of ten. The combined risk though is not adding them together and coming up with fifteen but its closer to fifty so if you look at the combined risk it's fifty in comparison to the sum of the individual risks of fifteen so you have an interactive effect which is thirty-five and by definition you cannot separate that out into the individual effects …." 61 Professor Henderson noted that the interactive effect was not medically explained, but appeared capable of theoretical explanation. He stated (p 111 (5)): "A number of theories have been put forwards but the two for which there is good supporting evidence are that in the first place, the carcinogenic components, that is the particular fraction of tobacco smoke can be absorbed onto the surface of asbestos fibres which are airborne so that what the individual inhales is an asbestos fibre coated with tobacco smoke carcinogens and the asbestos fibre can then deliver the carcinogens in tobacco smoke plus their own carcinogenic properties into airway of epithelial cells at higher concentration than would otherwise be the case. The other model and again there is good evidence for this is that tobacco smoke impairs and partially paralyses the cilia which are involved in clearance of dust and other particles from the lungs so that the tobacco smoke actually impairs the clearance of asbestos fibres from airway tissues and Churg and Stevens found that the concentration of amosite fibres in the bronchial walls of cigarette smokers was up to six times greater than the same concentrations [sic] in similarly exposed individuals who were not smokers and the differences were even greater for chrysotile fibres, up to fifty-fold difference. So that you seem to have both a concentration of asbestos fibres in the tissues at which the cancers arise and there is evidence that the asbestos enhances the delivery of the carcinogens in tobacco smoke into those tissues as well as exerting their own carcinogenic properties." 62 In the end, Professor Henderson himself was not anxious to place too much weight upon a mechanical application of the Helsinki Criteria. The following informative exchange took place towards the end of his cross-examination (p 142 (20)): "Q. … Do you agree with the proposition that attribution of increase of risk due to a cause is very fact sensitive in these asbestos-related lung cancer cases? A. I think it is. I mean even if one has – if one looks at tobacco smoking alone the chance of even a heavy smoker developing lung cancer is probably one in ten, so most heavy smokers still don't get lung cancer. The chance of an asbestos exposed person getting lung cancer is also quite low. The chance of somebody getting asbestos exposure [lung cancer?] when sustaining both patterns of exposure is greater but still reasonably low. So that there are many imponderables. All one can do is to say on a common sense basis taking into account what is known about asbestosis, equivalent levels of exposure, even lower levels of exposure, it's probable … each of tobacco smoke and asbestos have made a causal contribution towards the lung cancer, plus other unidentified factors." 63 After discussing the value of reliance on estimates of exposure prepared by the occupational hygienists, Professor Henderson stated (p 145 (35)): "Well I think both are subject to substantial imprecision, being retrospective estimates of exposures that occurred 20 or 30 years ago and therefore I've tended to base my assessment on other factors, for example the work history and my encountering cases of asbestosis among a similar workforce similarly exposed." 64 The cross-examiner further put to Professor Henderson (p 150): "Q. If Dr Francis is wrong and the cumulative dose inhaled is less than she suggested, that means conclusions to the extent you relied upon her would need to be modified? A. Well, if in fact the true inhaled dose were less than her estimates, then the risk associated with those cumulative exposures would be less. Equally, if the dose inhaled were more than Mr Pickford's, then the risk would be increased in comparison. And this is one of the reasons why I have simply adopted a very broad-brush approach, saying well I've done work on the basis of the work history, I've compared it with similar cases in my files and taken into account an editorial published by William Weiss recently. He basically said, 'Well the risks of lung cancer are increased in those worker groups where there are cases of asbestosis'. And I think that's a reasonable broad-brush approach." 65 Professor Henderson noted that Weiss' paper had been subject to "severe criticism" but, after giving a reference to the paper, noted that the criticism was on the basis that he had underestimated the risks: p 151(10). The cross-examination continued: "Q. What I'm trying to do here is just understand the tests that you applied. Are you saying that because these men were waterside workers then asbestos made some kind of contribution to their contraction of lung cancer? A. I think that it imposes a probability that that was the case provided that these people are representative of the cohort or group of waterside workers. And the argument is encapsulated in the following passage of text, Weiss argues that increased death rates or risks of lung cancer occur in cohorts where asbestosis also occurs. But this does not mean that asbestosis and lung cancer must occur seriatim in the same individual. All the data indicate is that lung cancer death rates are raised in cohorts where asbestosis occurs in some individuals not necessarily those who develop lung cancer. This observation is equally explicable by a dose response effect for both asbestosis and lung cancer without a direct fibrous to cancer linkage." Her Honour's reasoning with respect to relative risk 66 Two issues of fact were critical to the outcome of these cases. One was the availability of an inference that each of the workers was exposed to a level of asbestos dust sufficient to achieve a relative risk of at least 2 and thus at least a 50% chance that their lung cancer was asbestos-induced. Secondly, since all three men were regular smokers over lengthy periods up until their lung cancers were diagnosed, it was necessary that there be a factual basis capable of supporting the conclusion that asbestos fibre, more probably than not, contributed to the lung cancers. The fact that there was an interactive effect was widely accepted by the experts. The preponderance of evidence accepted that it was a multiplicative effect (or close to it) so that the existence of a relative risk with respect to asbestos of 3 and a relative risk with respect to smoking of 15 would produce a relative risk approaching 45 with the combination of both exposures. 67 What was not entirely clear from the evidence was whether the synergistic effect operated universally or only in the excess of cases over that figure which would be achieved by adding the two effects (in the example, 27, being the difference between 45 and 15 + 3). However, there was no suggestion in this Court that some error arose as a result of this uncertainty. It followed that it was open to her Honour to conclude that, given the available biological and physical explanations, the two carcinogens probably combined, each making a material contribution to the individual carcinomas. 68 Her Honour noted the evidence of Dr James Leigh that, "whatever the level of smoking, smoking and asbestos exposure are indivisible in the causation of an individual lung cancer, and any asbestos exposure multiplies the risk of lung cancer due to smoking by some quantity greater than one": at [102]. Accepting for present purposes that it was open to her Honour to accept that opinion, there was material which would justify the finding that where smoking and asbestos exposure coincided, asbestos made a material contribution to the disease in each case. 69 Some of the experts sought to apportion the relative effects of cigarette smoking and asbestos, even where they worked interactively. As the mechanism of interaction was not known, that appears to have been an artificial exercise and one which Professor Henderson and others considered flawed. Indeed, as the proponent of the mathematical model, Professor Berry said in evidence, in a passage set out by her Honour at [59]: "In fact often in my reports I put an extra sentence here and say in one sense it is impossible to do this because in the medical model they're closely linked together … but if it were required to do it for the purpose of compensation, given that two defendants don't have a joint bank account, as it were, then this is the method of doing it. But it's not a biological model." 70 The empirical basis upon which the apportionment exercise was undertaken was not explained in the evidence. Its relevance was not explained either in the evidence or in this Court. If it were thought to bear some relationship to the materiality of the contribution provided by asbestos, that contention was not relied upon in this Court, nor is its operation self-evident. 71 It may be that, underlying the appellant's argument in this Court, was the proposition that for a pathological condition to be reasonably attributable to a dust disease, the inhalation of dust must be a major or predominate cause and not merely a material contribution. However, that proposition was not expressly put and need not be addressed further. 72 This brief synopsis of the evidence and the reasons of the trial judge indicates the basic flaw in the appellant's core submission. Her Honour did not ignore the evidence of the causative effects of smoking; rather, that was not the issue to which the statute directed her attention. As she correctly identified, the statutory test required the Court to determine whether it had been shown on the balance of probabilities that exposure to asbestos dust materially contributed to the dust disease, namely in this case the lung cancers. One factor can materially contribute to an outcome even though, relative to another factor it has a minor effect. All that is required is that the effect be "material". That required an evaluative judgment on the part of the Court. Such a judgment, based on available evidence, could not readily be the subject of challenge in an appeal limited to a decision in point of law. Admission of evidence: Helsinki criteria 73 To complete the foregoing analysis, it will be necessary to return to the reasons given by the trial judge. The appellant submitted that the reasons were inadequate in a manner which gave rise to a ground of appeal under s 142N. However, it also submitted that her Honour was in error in admitting: (a) affidavits provided by the workers, and (b) reports of Dr Francis. This question should logically be addressed first, now that the evidence can be placed in context. 74 Although it was not identified in the notice of appeal, nor in the appellant's written submissions, in the course of the oral argument the appellant sought to rely upon an additional complaint, namely objection to the admission of evidence as to the "Helsinki Criteria". It is quite doubtful, however, that this was truly an objection to the admissibility of evidence. The objection, as explained in the course of oral argument in this Court, was that "it wasn't a proper legal test" for causation: Tcpt, 17/11/09, pp 22-24. Rather, the complaint was the way in which her Honour applied the criteria at [147], where her Honour stated: "Despite the criticism of the Helsinki Criteria, for example by Mr Rogers, and despite the opinion of Dr Berry that 50 fibre/ml years is required for attribution, the Helsinki Criteria of 25 fibre/ml years remains the preferred model of most of the experts. I propose to adopt those criteria in preference to the opinion of Dr Berry. If it be necessary to find the number of fibre/ml years at which the risk of contracting lung cancer is doubled, on the preponderance of the expert evidence I accept the Helsinki Criterion of 25 fibre/ml years." 75 In the course of the tender of Professor Henderson's reports, senior counsel for the appellant objected to Professor Henderson expressing an opinion as to whether or not Mr Smith satisfied the Helsinki Criteria for determining a relative risk of 2 from the standard measure of exposure to asbestos dust. He stated that the "objection that we want to take is this, the application of the Helsinki Criteria as a matter of law is an issue": Tcpt, 07/02/07, p 10 (55). 76 Counsel returned to the issue later on the same day (Tcpt, p 81 (45)) stating: "The idea that there would be applicable to determine causation in New South Wales and especially under the Workers' Compensation Dust Diseases Act 1942 the application of either Helsinki criteria or AWARD criteria, I object to that. AWARD stands for Adelaide Workshop on Asbestos Related Diseases and again it's a compensation criteria [sic] which Professor Henderson refers to. We object to any evidence which would suggest that that would be applicable in New South Wales, but that's a legal matter." 77 Although the "objection" was based on relevance, there was no dispute that "relative risk" was a means of measuring the probability of a particular cancer being caused by a particular agent. However, relative risk was merely a statistical calculation. To achieve a particular outcome, it required factual input. It being common ground that the likelihood of asbestos causing lung cancer was dependent upon intensity and length of exposure, it was clearly a matter for expert evidence as to how the intensity and the extent of the exposure should be measured and as to what measurement would permit an inference of probability of causation. The Helsinki Criteria constituted a statement of opinion by a group of identified experts as to the appropriate level of exposure to produce a relative risk of 2. Not all the experts agreed with it, as her Honour noted at [147]. 78 Because her Honour took it into account, it can be assumed that the level of exposure identified in the Helsinki Criteria was treated as a relevant expression of expert opinion on a factual matter, not a legal test. As evidence it was not irrelevant. The objection was not based upon any other matter going to the admissibility of expert opinion evidence pursuant to s 79 of the Evidence Act. For this reason the additional ground of appeal (which was never adequately formulated) should be rejected. 79 Furthermore, it was a matter which had no material effect on the outcome. For reasons which will be referred to below, the causal effect with respect to Mr Smith was accepted on a different basis. In relation to Messrs Munro and Seymour, her Honour estimated that the total exposure was at least 70 fibre/ml years and 60 fibre/ml years respectively. These figures exceeded the Helsinki criteria and would have produced a doubling of the risk even, as her Honour noted at [236], on Dr Berry's approach. 80 It should be added that the difficulty in exposing the flaw (or flaws) in the appellant's reasoning was greatly increased by the failure of the appellant to identify this matter as a ground of appeal at any stage prior to the hearing of oral argument. In this, as in other matters, the Court was provided with less than the assistance to which it was entitled, to say nothing of the potential for prejudice to the respondents. Admission of evidence: Evidence Act, s 135 81 It is not in dispute that the erroneous admission of evidence over objection is a ground of appeal under s 142N, which permits an appeal not merely in relation to an award of the Court in point of law, but "on a question as to the admission or rejection of evidence". However, much of the case presented by the appellant, purportedly in reliance on this ground related to the weight given to the affidavits of the workers and, consequentially, to the evidence of Dr Francis. That is not to say that the weight to be given to the evidence was irrelevant to the question of its admission. Section 135 of the Evidence Act, which was relied upon as a basis for rejection of the affidavits of the workers, reads as follows: " 135 General discretion to exclude evidence The court may refuse to admit evidence if its probative value is substantially outweighed by the danger that the evidence might: (a) be unfairly prejudicial to a party, or (b) be misleading or confusing, or (c) cause or result in undue waste of time." 82 At least in principle, the less the probative value of the proffered evidence, the greater the likelihood that such value may be "substantially outweighed" by one of the specified dangers. However, the section requires a balancing exercise and the appellant failed to identify the specific elements in pars (a), (b) and (c) which were relied upon. Further, little attention was given in the appellant's submissions to the nature of an objection to the admission of evidence under s 135 in the case of a civil trial conducted by a judge alone. 83 The section commences with the assumption that the proffered evidence is otherwise admissible: see Dyldam Developments Pty Ltd v Jones [2008] NSWCA 56 at [78]. The affidavits of the deceased workers were admissible pursuant to s 63 of the Evidence Act because they contained representations as to the circumstances of the work environment by persons who were unavailable to give evidence. The importance of noting the assumption that the evidence is admissible is to avoid reliance on s 135 being used to reintroduce common law attitudes to previously inadmissible evidence: see Papakosmas v The Queen [1999] HCA 37; 196 CLR 297 at [93] (McHugh J). (See also the doubts expressed as to the appropriate use of such material in ACCC v Australian Safeway Stores Pty Ltd [1999] FCA 1269, by Goldberg J at [28]-[29].) 84 There will always be a degree of prejudice to another party where the maker of the statement is unavailable for cross-examination. Generally speaking, that degree of prejudice is treated by s 63 as not rendering the admission of the material necessarily unfair. The effect of ss 63 and 135 in combination is that the party opposing admission will generally bear the persuasive burden of satisfying the Court that any probative value is substantially outweighed by the danger of unfair prejudice to it. At least in a judge-only civil trial, in practical terms the opposing party will also bear the persuasive burden in showing that the evidence might be misleading or confusing or would cause an undue waste of time. Admission of evidence: Dr Francis' reports 85 The submissions for the appellant focussed on the probative value of parts of the evidence on the basis of an assessment of the whole of the evidence undertaken by the trial judge in her reasons for judgment. That was an impermissible attempt to review the merits of the case. If there were a basis for appeal against the admission of evidence, that must be assessed by reference to the precise terms of the objection taken and the ruling made. If subsequent events in the course of the trial lead the objecting party to renew or reopen its objection, those events may become relevant: otherwise, the subject matter of the appeal should be restricted to a consideration of the objection and the ruling. 86 The objections to evidence were dealt with on the second day of the trial. The appellant had not reduced its objections to writing, so they were dealt with as they arose: Tcpt, 07/02/07, p 3 (45). Each of the three cases was taken in turn, although the elements of commonality meant that the evidence in each was quite similar to evidence in the others. The process commenced with the evidence relevant to the deceased Mr Smith: Tcpt, p 4 (15). 87 In order to identify the subject matter of the appeal, no particulars having been provided in the notice of appeal, it is necessary to glean the relevant documents from the written submissions. In relation to the case concerning Mr Smith, the first evidence to which objection was taken were reports of Dr Eva Francis of 8 July 2002 and 8 December 2006: for tender, see Tcpt, 07/02/07, p 21 (50). Dr Francis prepared two reports relevant to Mr Smith. The appellant took objection to three passages in the first report and took no objection to the second report, being that dated 8 December 2006. In written submissions, the appellant stated that it "objected to the reports' admission into evidence": written submissions, par 65. That statement was supported by reference to the transcript, but was in its terms grossly misleading. 88 It is convenient to address together the objections taken to the first report of Dr Francis dated 8 July 2002. The first objection was taken to material contained in a section of the report headed "Exposure levels". Dr Francis stated: "(i) For the work of Mr Smith on the waterfront, I estimate the average daily airborne asbestos exposure in the period from 1970 to about 1978 to have been 25 fibre/ml whilst unloading asbestos from the holds of the ships. … (ii) I estimate the average daily airborne asbestos exposure in the period from 1970 to about 1978 to have been 10 fibre/ml whilst stacking asbestos bags on the wharf. This contributes 1.5 to 3 fibre/ml-years over 7.5 years." 89 Dr Francis was an occupational hygienist and there was no suggestion that she was not an appropriately qualified expert, able to provide assessments of levels of exposure to asbestos. The complaint in relation to these two passages was that she had failed to reveal the basis upon which her estimates were made. The objection taken to the first passage was that immediately following the sentence set out above at (i), Dr Francis had continued: "I have taken an estimate from the 16 fibres per ml (fpml) which I measured on 11 January 1972 unloading chrysotile in the upper hold of the Dimos Halcaussis, and the 5 fpml (unloading plastic-lined bags of amosite) to 45 fpml (unloading chrysotile from refrigerated lockers) reported by G Major, occupational hygienist, of the SPHTM Sydney Uni in the 1969 Asbestos on the Waterfront Report to the NHMRC." 90 In making the objection, senior counsel for the appellant (Mr Watson SC) identified the objection in the following terms (Tcpt, 07/02/07, p 22 (5)): "WATSON: On the basis that – well on the basis of the so-called basis rule. What Dr Francis says is that she estimates a concentration of fibres of 25 fibres per millilitre and it's not possible – HER HONOUR: Well isn't that what she's employed to do? WATSON: Well except even if one looks at the next sentence, Dr Francis herself referred to her own findings of 16 fibres per millilitre. HER HONOUR: When she actually was there. WATSON: Yes. HER HONOUR: Well doesn't she explain why she has increased it. WATSON: No." 91 If the gravamen of the objection was that she did not explain the mathematics, it might be understandable: however, it is clear that she did identify the basis of her calculation, being her own assessment and that of Mr Major. Further, in broad terms, she summarised her knowledge and understanding of the circumstances of Mr Smith's exposure. It is not correct to say that the basis for her opinion was not disclosed. It was open to the appellant to explore the detail of the calculation in cross-examination, as it did. 92 The second objection taken by Mr Watson concerned what appears to have been a summary of Mr Major's report. Mr Watson stated (p 23 (5)): "WATSON: Yes I object to those being accurate summaries of the reports. That said Your Honour doesn't need to – HER HONOUR: Well do you say they're not. WATSON: They're not. Your Honour doesn't need to rule on this, it's just that it gives me the opportunity to put them in in due course." 93 It does not appear that this constituted an objection to evidence upon which her Honour was required to rule. If the appeal extended to this material (which is quite unclear) it should be rejected. 94 The third objection concerned the paragraph (ii) as set out above. The objection was again stated to be "the basis rule" although no explanation was given and the objection was noted. Understandably, no complaint was made about that course at the time. The complaint appears to be that her Honour failed in her final judgment to rule upon the objection to that evidence. 95 In the course of her oral evidence with respect to Mr Munro, Dr Francis was invited to explain a very similar calculation to that set out in respect of Mr Smith at paragraph (i). During her explanation, Mr Watson stated (Tcpt, 12/02/07, p 238 (20)): "Although Dr Francis did so for the reasons I explained [sic] I'm not taking the objection again nor cavilling with your Honour's ruling but just pointing out that statement of evidence just given is precisely the kind of material which I would need to get somebody to look at. But I think I can." 96 The examination in chief of Dr Francis was primarily directed to her report concerning Mr Munro, in which she appears to have undertaken similar calculations to those undertaken with respect to Mr Smith. Her report, dated 24 September 2001, was not included in the appeal books prepared by the appellant, but was handed up by counsel as part of a bundle prepared for the purposes of oral argument. Dr Francis' attention was directed to her calculation of exposure levels, based on the same material as that provided in her report in respect of Mr Smith. Her explanation is lengthy and is set out in the transcript of 12/02/07 at pp 241-242. She was not required to repeat the explanation in relation to the similar calculations in the reports relating to Mr Smith and Mr Wales. (Aspects specific to Mr Smith's case were dealt with in the transcript at pp 249-250.) Unsurprisingly, virtually the whole of the lengthy cross-examination of Dr Francis was directed to her estimates of exposure levels and the material upon which she based her estimates. 97 Not all of the discussion in the course of the trial was taken down, and it is not entirely clear how the issue of admissibility was addressed at all points. On 14 February 2007 counsel for the respondents referred to the question of "renewal", a course to which objection was taken: Tcpt, p 407 (15). The matter in fact raised at that stage by counsel for the appellant related to Dr Francis' reference to an article, which counsel for the respondents agreed to clarify. 98 The following day, after further discussion, her Honour clarified the position in the following terms (p 420 (40)): "Yes, I think Mr Watson has made his position clear from the outset and I did admit it on the basis that Dr Francis' opinion had to be established and if they have been they have been, if they haven't then part or all of her opinion, I would think probably more likely to be part, falls down, yes. Is that sufficient for everyone's purpose?" 99 Once it became clear that her Honour had accepted the bases of Dr Francis' opinions, no further reasons were called for. The complaint that she did not expressly rule on the outstanding objections is a complaint without substance. 100 In any event, the trial judge dealt with the evidence of Dr Francis in her reasons at [149]-[159]. Most of that discussion related to her estimates of exposure levels. Her Honour referred to her evidence of testing on the ship Dimos Halcaussis at [151]-[152] and to her understanding of Mr Major's report at [153]. At [155], her Honour stated: "During her evidence, Dr Francis described the 'values' – being the concentration of fibres/ml (or cc) as being 'estimates' and said (transcript p 286) 'Even when they're measured they're still estimates.['] She explained that the measurements she took in the early 1970's were only estimates because the samples were taken in an area where a worker or workers were working and said (transcript p 291) 'If they (referring to the sample measuring device) are in fact a fixed position sample, it gives you an indication of the exposure that the workman would have when he walked through those areas rather than when he physically personally disturbed the asbestos because general area samples generally give you – nearly always give you a lower reading than a personal sample near the breathing zone of the actual workman when he's working.'" After discussing the different figures arrived at by the defendant's occupational hygienist Mr Pickford, her Honour stated her preference for Dr Francis' estimates: see at [58] above. 101 Although it is correct to say that her Honour never expressly ruled on the objection to the admissibility of Dr Francis' evidence, and although the appellant maintained its objection, its substance had diminished, if not evaporated, by the end of the oral testimony given by Dr Francis. Her Honour's reference to the evidence indicates that she accepted it and, implicitly, had overruled any outstanding objection. The complaint that there was no express ruling is without substance. Admission of evidence: affidavits of workers 102 As with the appeal with respect to the admission of Dr Francis' reports, there was no indication in the notice of appeal as to the grounds with respect to the workers' affidavits, and the written submissions were misleading. The submissions stated that the appellant "objected to the admission of the affidavits" (par 41) and that the basis for objection was s 135 of the Evidence Act" (par 43). Both those statements were inaccurate. 103 The first of the affidavits was that of Mr Smith. Objection was not taken to the affidavit, but to four paragraphs therein. Three of the objections related to the same factual estimate, namely that he had worked unloading cargos of raw asbestos "for between 8 to 10 cargos per year on average". The objection was that there was or would be other evidence which contradicted that estimate. Counsel stated (Tcpt, 07/02/07, p 34 (15)): "Now it might be that your Honour can't really make a judgment about whether this evidence is reliable or not until such as time as your Honour hears the other evidence and it might even then albeit [sic] a question of weight, but I take the objection now because without Mr Smith here we did directly wish to challenge those estimates." 104 The fourth objection was to a paragraph in which Mr Smith set out his smoking history, again the objection being a statement of intention to rely on other material which was said to be inconsistent with that history. 105 It is possible that the objection was intended to invoke the discretion under s 135 of the Evidence Act, although that section was not referred to and, as senior counsel for the respondents stated, each of the workers was entitled to make an estimate and if there were contrary evidence it was a matter for her Honour to assess: Tcpt, p 34 (50). 106 Whenever disputed documentary evidence is submitted, where the author is unavailable for cross-examination, the Court will be required to assess the reliability of the evidence without the contrary material having been put to a witness in cross-examination. That difficulty, especially in the case of a trial before a judge only, does not, in the present circumstances, engage the discretion conferred by s 135. There was nothing inherently prejudicial in the nature of the evidence. The evidence itself went to a critical issue in the case. The evidence was properly admitted. Similar objections were raised in relation to the affidavit of the late Mr Munro (Tcpt, 07/02/07, p 39) and the appeal in respect of that matter should be rejected for the same reason. 107 The complaint expressly based on s 135, related to a different matter, namely that there were quite striking similarities between the affidavits of Mr Munro and Mr Wales. Her Honour ruled on the objection: Tcpt, p 80 (15)-(55). After stating that she did not intend to reject the affidavits, her Honour continued: "I know I'm only asked to reject as so incredible as to be prejudicial under s 135 on the basis that although there are unfortunately great similarities in a number of the paragraphs, in particular in the wording and phrasing, I don't think I can infer that that is because of the lack of credibility of the maker of the affidavit. I would think I could infer due to the use of word process material by the solicitor who drafted the affidavit, however, the maker of the affidavit only has to adopt what it is said. It is very unusual for the maker of an affidavit to use, again perhaps unfortunately in certain circumstances, his or her own words or we'd be left with ums and ahas and completely ungrammatical and difficult to read documents. However it does raise some questions of course of what versions, if there are to be a number of versions, are to be preferred. It does appear that both of these gentlemen at the stage that they made the affidavits were not well men. They had certain instructions given to the solicitor and he prepared affidavits. I also take into account that both of the gentlemen worked at similar times, not identical, and at the same waterfronts. The complaints made about the descriptions for example of the appearance of asbestos and the use of the other descriptions of the asbestos, obviously there may be some questions of weight as to the emphasis placed on some of these matters in the two affidavits if they are to be compared and contrasted with other histories, but I don't see that they are to be viewed for the reasons I've just briefly referred to and they're certainly not all of them, rejected as so affecting the credibility of the makers of these affidavits that they should be held to be inadmissible." 108 The written submissions on the appeal sought to challenge this decision on two broad bases. One was described as the sheer improbability of the accuracy of the affidavits, particularly in relation to the number of days on which each deponent says that he unloaded asbestos cargoes. That complaint was similar to that raised in relation to estimates given by Mr Smith and should be rejected for the same reasons. 109 The second basis of challenge was that her Honour accepted the evidence of the workers in her final judgment, on factually flawed bases. That submission was misconceived: it sought to attack the factual findings made by the trial judge, not her Honour's ruling on the admission of the workers' affidavits. 110 Thirdly, there is passing reference in the written submissions to the fact that the affidavits should be characterised as "inherently unreliable given some remarkable similarities between them": at par 56. It was further said that her Honour dismissed the argument in part upon the basis that the workers were "very ill" and in part on the basis that "their accounts were corroborated by other sources". The phrase "very ill" did not come from the ruling set out above and the statement that they were "not well men" was merely an indication as to the inference her Honour drew as to how the affidavits had come to be prepared in the form which they bore. That language does not demonstrate error, but rather a rational assessment of the probative value of the material in the circumstances in which the deponents were not to be cross-examined. Her Honour did not rely upon corroboration from other sources in making the ruling. 111 It is doubtful whether any of the contents of the affidavits of the deceased workers could be described as relevantly "misleading or confusing" to the Court. The general flavour of the affidavits may be obtained from the lengthy extract from the affidavit of Mr Smith set out by the trial judge at [49]-[50]. It does not appear to be misleading or confusing, nor did counsel to seek to rely upon this as a basis for rejecting the evidence. Their admission, assuming they had probative effect, would also be unlikely to constitute a waste of time, let alone an undue waste of time, unless the probative value was so low that it would render unnecessary cross-examination of Dr Francis, who relied in part upon their evidence. The gravamen of the concern, not fully articulated, was apparently potential prejudice to the appellant. 112 The challenge to the admission of the workers' affidavits must fail. As explained above, the focus of the challenge was the unreliability of the evidence and its inconsistency with other material presented by the appellant. Accepting that those arguments may affect the probative value of the affidavits, they do not themselves demonstrate either that there was a danger of unfair prejudice to the appellant or that such a danger "substantially outweighed" the probative value. Her Honour, nevertheless, analysed the reasons for the similarities between the two affidavits and the significance which might be attached to them. Her acceptance of that material, confirmed in the final judgment at [32], was not shown to be erroneous. The ground of appeal based on this challenge should be rejected. Ground 2: challenges to factual findings 113 Amongst the complaints raised in the written submissions was the proposition that the trial judge "not only admitted the affidavits [of the workers], but gave them full weight in preference to other evidence": par 42. This was an unpromising start to a submission purporting to identify errors of law. 114 The appellant disputed the workers' claims of the number of days on which they unloaded asbestos during an average year. The Board made submissions, based on evidence "as to why the workers' affidavits could not be accurate": submissions, par 47. The appellant acknowledged that the trial judge expressly referred to its submissions at [64]-[65], but contended that the trial judge "did not deal directly with the submission", a complaint which was inaccurate. For example, part of the appellant's submission, repeated in this Court, was that Dr Francis did not support the estimates of the numbers of occasions upon which workers were exposed to asbestos, which, in a 1971 letter to the NSW Department of Health, she had said occurred "only spasmodically" during the year. Dr Francis continued: "Thus a shipment of asbestos is generally unloaded and delivered in one week and there may be one shipment a month or sometimes less." That, the appellant contended, amounted to "something like 60 days per years, allocated at random amongst hundreds of gangs". 115 That submission had a number of aspects which her Honour addressed. For example, her Honour noted the evidence of Mr Robson which was inconsistent with random allocation of work: at [66]. Secondly, her Honour did not accept the proposition that Dr Francis could be relied upon as having expert knowledge of the extent of exposure. Her Honour stated at [154]: "Although Mr Watson attempted to establish during cross-examination that Dr Francis was knowledgeable about the workings of the waterfront, and in particular the way in which waterside workers were allocated work and the way in which gangs operated, it was relatively clear that, although she had observed the process of unloading asbestos from ships in the early 1970s, she had no other specialised knowledge of the workings of gangs or of the waterfront in general. Although she made a number of concessions, based, as I understand it, mainly on logic, she did not concede that she knew anything about the allocation of the work on the waterfront or the manner in which gangs distributed the work among their members." 116 This challenge to the judgment not only addressed no point of law but was, in its own terms, without foundation. 117 As noted above, no reference was made in the course of the submissions to a ground identified in the notice of appeal as "wrongly relying upon expert evidence": ground 2(e). That imprecise challenge may be put to one side on the basis that it was not pursued. However, there were two further challenges, each of which referred to "making or purporting to make findings", either: (a) in the absence of evidence to support the findings, and (b) in the absence of providing adequate reasons for making the finding. 118 A degree of uncertainty arose in this context from the various meanings which could attach to the concept of "findings". Broadly speaking, a "finding" could involve a reference to: (a) findings of primary fact; (b) inferences drawn from primary facts, or (c) the ultimate finding on which judgment was based. 119 This picture was complicated further by the written submissions which, in blithe disregard of the scope of the notice of appeal, asserted that there were "a number of instances where the trial judge simply failed to engage with the issues which were raised": written submissions, par 45. On one view, that could have been taken as a complaint that necessary findings were not made. In the context, it should probably be understood as referring to evidence which was not addressed in making the required findings. 120 The ultimate issue for determination could be identified in the following terms: did the exposure of each worker to asbestos dust whilst working on the waterfront materially contribute to the lung cancer from which he died? There are of course a number of assumptions contained in that question, such as the fact that the worker died from lung cancer, but these were not contentious. Further, the question must be understood as requiring that causation, in the sense of material contribution, be established on the balance of probabilities. 121 Her Honour concluded that the relevant test was satisfied: Judgment, [237]-[238]. It could not be contended, nor was it in terms contended, that there was no evidence capable of supporting that conclusion. Rather, the appellant contended that underlying the ultimate conclusion were a number of inferences which were not properly available because they were based on evidence which "should have been given no weight", which "could not have been accurate" or which could not have been accepted without rejection of other evidence which appeared not to have been considered and rejected. 122 The language adopted in the course of the submissions failed to come to terms with the basis upon which an absence of evidence could constitute an error of law. To accept some evidence and to reject other evidence could, at best from the point of the appellant, amount to a "wrong finding of fact", which does not constitute an error in point of law: Australian Broadcasting Tribunal v Bond [1990] HCA 33; 170 CLR 321 at 356 (Mason CJ). At least where the legal question has been correctly identified, the failure to deal with contradicting evidence may involve inadequacy of reasons or possibly a breach of procedural fairness, although the latter issue was not raised in the present case and arguably could not have arisen within the statutory appeal. 123 What in fact was done amounted to the subdivision of issues into component parts, the appellant in effect arguing that each part constituted a link in a chain, so that if evidence to support any particular inference were missing, there would be no evidence to support the ultimate conclusion. However, in the present case, that approach was of limited value. The question of causation was inherently based upon a number of concurrent factors, each incorporating a significant level of uncertainty. It was not a case involving a series of links in an essential chain of fact-finding. 124 There remains for analysis the challenge to inferences drawn from primary facts. In Azzopardi v Tasman UEB Industries Ltd [1985] 4 NSWLR 139 at 156, Glass JA identified as the first stage of the judicial process, "determining the facts by way of primary findings and inferences". Primary facts may, of course, be inferred from particular evidence. However, the process of drawing inferences from such facts is a discrete exercise. Thus, if the driver of a car gives evidence that he put his foot on the brake pedal to no effect, it may be inferred that the brakes failed. The cause of the failure may involve a further inference of a different kind. The further inference may be that there was a mechanical defect in the car. In some circumstances that inference can be drawn on the basis of general experience and commonsense; in other cases it may depend upon inquiry into the operation of the mechanism (if available) or it may depend upon expert assessment. 125 The inference that one event caused another because of a temporal relationship will rarely be available, absent some element of connection between the two events. (A mere temporal connection between an increase in the export of apples from Canada and an increase in the rates of lung cancer in the UK is unlikely to demonstrate a causal connection.) In many cases there will be a question whether commonsense can provide an answer or whether an inference can only be drawn on the basis of specific expertise. The application of the well-known statement of McHugh J in Chappel v Hart [1998] HCA 5; 195 CLR 232 at [27] that "[i]f a wrongful act or omission results in an increased risk of injury to the plaintiff and that risk eventuates, the defendant's conduct has materially contributed to the injury that the plaintiff suffers whether or not other factors also contributed to that injury occurring", may well depend upon which of the categories is invoked. Indeed, the appellant's argument in the present case depends upon the falsity of that approach in relation to smokers who are exposed to asbestos (both agents which increase the risk of lung cancer) where lung cancer has materialised. It is doubtful whether, in such a case, "commonsense" can permit the inference that exposure to asbestos dust probably contributed to the disease. Similarly, the reference to "commonsense" approved in March v Stramare (E & MH Pty Ltd) [1991] HCA 12; 171 CLR 506 at 515, taken from the judgment of Lord Reid in Stapley v Gypsum Mines Ltd [1953] AC 663 at 681 may not operate uniformly in different kinds of case. In some cases such an approach may be inappropriate. There will then be a question as to whether inappropriate reliance upon commonsense to draw a causal link can constitute an error of law in circumstances where illogicality in the drawing of inferences is said not to give rise to an error of that kind. 126 In some circumstances the reasoning of the trial judge may reveal legal error. Thus, if the evidence revealed, as the appellant claimed in the present case, that the chance of the lung cancer being caused by asbestos dust was only a small fraction of the chance that it was caused by smoking, but the judge accepted that the causal link was established, the reasoning may demonstrate that the Court had failed to determine causation on the balance of probabilities. Illogical or perverse reasoning may permit the inference that there has been an erroneous application of legal principle, rather than an unexplained lapse into illogicality. 127 Thus, in order to determine the correct approach to the question of causation, it is necessary to identify the particular issues which arose in the matters before the District Court. The available questions may include the following: (a) does evidence or experience support a causal connection between temporally consecutive events? (b) if so, what are the preconditions for establishing the connection? (c) is it known whether the causal capability eventuated in the particular case? (Other questions may be envisaged.) 128 These particular questions are sometimes referred to as "general causation", causal mechanism and "specific causation". In Seltsam Pty Ltd v McGuiness [2000] NSWCA 29; 49 NSWLR 262 the worker suffered (and died from) a renal cell carcinoma following exposure to asbestos dust, whilst working for the appellant. "Commonsense" may suggest that exposure to a known carcinogen, followed by a carcinoma would give rise to the inference, on the probabilities, that the exposure caused the condition. However, commonsense may be an inadequate guide. A commonsense, but uninformed, view could gain legitimate support from scientific evidence that the carcinogen was known to enter or pass through the kidneys. Further support may be given to the potential inference by expert evidence of a plausible explanation of a mechanism, although the operation of the mechanism has not been observed. That may provide an element of "biological plausibility": see Spigelman CJ at [41]-[42]. Biological plausibility may be strengthened by observation of a known mechanism in laboratory experiments or by epidemiological studies. These are matters for expert analysis and explanation, not commonsense. 129 In Seltsam, the Chief Justice noted the manner in which epidemiological evidence could be used. (Indeed, many of the comments would extend to other forms of medical science.) However, his Honour commenced with the proposition that the establishment of a possibility would not satisfy the common law test requiring proof on the balance of probabilities in civil litigation: at [80]. That comment is equally applicable in the case of a statutory claim which depends upon the civil standard of proof. Although not designed to determine the cause of a particular condition in an individual, epidemiological evidence allows for a probabilistic or stochastic approach (to use the language of Professor Henderson), as a form of circumstantial evidence, capable of combination with other evidence, in order to establish causation in a specific case: see Seltsam at [89]. As noted by Spigelman CJ in Seltsam at [67]: "Most epidemiological studies identify the strength of an association by a measure called relative risk (RR). RR is defined as the ratio of the incidence of disease in exposed individuals compared to the incidence in unexposed individuals. If the relative risk equals 1.0, the risk in exposed individuals is the same as the risk in unexposed individuals. If the relative risk is greater than 1.0 the risk in exposed individuals is greater than the risk in unexposed individuals." 130 Statistically, it is only when the relative risk reaches 2 that the chance that the condition was caused by the identified agent is equal to the chance that it was caused by some other mechanism. Accordingly, where the relative risk is greater than 2, it may be said that the epidemiology will support an inference that the condition was more probably than not caused by the agent under consideration: Seltsam at [121]. Spigelman CJ, continued, at [137]: "In Australian law, the test of actual persuasion does not require epidemiological studies to reach the level of a Relative Risk of 2.0, even where that is the only evidence available to a court. Nevertheless, the closer the ratio approaches 2.0, the greater the significance that can be attached to the studies for the purposes of drawing an inference of causation in an individual case. The 'strands in the cable' must be capable of bearing the weight of the ultimate inference." 131 The analogy of "strands in a cable" may not operate where the epidemiological evidence is the only strand capable of supporting a claimant's case. However, his Honour's reasoning requires consideration of what is involved in the establishment of a relative risk. In particular, there are two elements which may reduce the significance for legal purposes of the attribution of 50% probability which flows only from a relative risk of 2.0. The first is that statistical analysis will involve a degree of potential error, so that, instead of a single figure, it might be more accurate to identify a range, together with the confidence level which is achieved at a particular point in the range. The studies routinely identify what is described as a "95% confidence interval". That is not necessarily a test which the law would apply in respect of causation. Secondly, it is not merely the uncertainty of the studies which must be taken into account, but also the uncertainties surrounding the individual to whom the risk analysis is applied in the course of the litigation. The difficulty, even the impossibility, of knowing with any degree of precision the intensity or duration of exposure to asbestos dust in respect of a deceased worker, prevents meaningful calculations being undertaken at any level of precision and allows for an element of evaluative judgment on the part of the trial judge. 132 In the course of cross-examination, counsel invited Professor Henderson to adopt, as a factor which might be taken into account a clinician's feelings about a case. Professor Henderson rejected the invitation (Tcpt, 08/02/07, p 129 (10)): "No, I don't like to take in clinicians' feelings. To me that is an unquantifiable, unmeasurable and unexaminable proposition. All I would say is one tries to develop as refined an approach to causation as one can, taking into account variation and exposures, variation in capacity to clear say carcinogens in tobacco smoke and asbestos, variation in individual predisposition to the disease." 133 Professor Henderson was among the experts decrying a mechanical use of relative risk in determining the probabilities in respect of the cause of the individual carcinomas. However, he did so on the basis of known uncertainty, and would not have supported an unscientific recourse to "commonsense". 134 None of these considerations demonstrates any error in the approach taken by her Honour to the question of causation. It is therefore not necessary to consider further the circumstances in which error in assessing causation might constitute an erroneous decision on the part of the District Court in point of law, for the purposes of the statutory appeal. Ground 2: inadequacy of reasons 135 In Day v SAS Trustee Corporation [2009] NSWCA 222 Giles JA (with whom Ipp JA agreed) considered that a failure to accord procedural fairness gave rise to a grievance in point of law, which was sufficient for an appeal under s 142N to succeed: at [72]. The alternative, minority, view, was that the appellant was required to identify an award or decision of the District Court in point of law, as being the subject-matter of the appeal: at [86] and [94]. In SAS Trustee Corporation v Pearce [2009] NSWCA 302 I expressed a doubt (with the agreement of Beazley JA) as to whether a failure on the part of the District Court judge to give "adequate reasons" for his decision could constitute a decision of the District Court in point of law for the purposes of s 142N: at [43]. 136 There is an abundance of authority in support of the proposition that a failure of a court to give adequate reasons for its findings constitutes an error of law: see, eg, Soulemezis v Dudley (Holdings) Pty Ltd (1987) 10 NSWLR 247. However, whether such a failure involves a decision of the court below in point of law is less clear. There may be circumstances in which it does, but those may be restricted to the case where the court or tribunal has expressly or implicitly decided that certain matters should not be dealt with in the reasons: see Pettitt v Dunkley [1971] 1 NSWLR 376 at 383-4, referred to in Pearce at [119]. 137 Further, there is something incongruous in the proposition that to reason illogically, even perversely, does not constitute error of law, but to fail to provide adequate reasons does. Decisions in point of law refer to the substance of the decision-making process and not merely its presentation. 138 The legal obligation on the part of a judge to give reasons for his or her decision derives from the nature of judicial power and the proper means of its exercise: Soulemezis at 278-279 (McHugh JA). Its role in modern jurisprudence has been to provide a mechanism of control where appeals are limited to questions or points of law or on grounds available for supervision by way of judicial review in the nature of prerogative relief. In relation to statutory appeals, limited attention has been given to the statutory context in which the matter has come before the Court. In relation to the supervisory jurisdiction, it is necessary to identify where the failure to comply with a legal obligation to give reasons fits within a scheme which does not permit review for illogicality in the reasoning process. Thus, a missed step in an argument, or the illogical drawing of an inference would not, on the latter approach, demonstrate reviewable error. 139 In circumstances where, as in the present case, the primary obligation of the trial court was to determine the matter on "the real merits and justice of the case", it may be thought that on review, inadequacy of reasons should take a secondary role to considering whether the real merits and justice of the case have been addressed and a decision made on that basis. That statutory context renders it inappropriate for this Court to conduct a critique of the written reasons, not to search for error otherwise revealed, but to address an amorphous standard of "adequacy". 140 The crux of the appellant's complaint is that her Honour gave 'inadequate' attention to the likelihood of the agency of smoking in causing the lung cancer. The basis of this complaint appeared to lie in the final paragraphs of her Honour's judgment where she identified the total exposure of the workers at a level sufficient to justify a finding that the relative risk arising from the asbestos exposure was more than 2. On that basis she found "that the asbestos exposure of all three deceased workers, in combination with each worker's smoking, made a material contribution to their lung cancers, from which each of them died": at [237]. 141 The reference to smoking in this context is not to be ignored; it is not treated as an alternative cause, but as an agent acting "in combination with" asbestos dust. That language harks back to her Honour's earlier statement of a number of propositions derived from the medical and scientific evidence which she clearly treated as beyond dispute: at [59]. The third proposition was that the "combination of the inhalation of asbestos fibres and tobacco smoking has a 'synergistic' or 'interactive' effect leading to a risk higher than the sum of the risks of each used independently". She further accepted that the interactive effect was either truly multiplicative or closer to multiplicative than additive. 142 These findings suggest that it was unnecessary to set out arithmetical calculations indicating the independent and interactive effects. Indeed, on the evidence that would not have been possible. Professor Berry produced calculations which sought to separate the interactive effects and attribute them to asbestos and smoking respectively. However, that exercise did not have a biological basis: see, eg, Dr James Leigh at [102] and at Tcpt, 15/02/07, pp 410-411. So much was also accepted by Dr Berry himself, in the passage set out at [69] above. Professor Henderson also said that, while there were various models for apportioning the causal effects of tobacco smoke and asbestos it was "an artificial exercise because by definition the interactive effect is not separable into the individual effects". He described the model by which apportionment was undertaken as sophisticated but that it was "inherently a flawed model". 143 The exercise her Honour undertook was to determine whether asbestos materially contributed to the lung cancer: for that purpose, it was not necessary to apportion contributions between asbestos and smoking so long as her Honour was satisfied that asbestos made a "material" contribution. As indicated above, there was ample evidence for her Honour to conclude, as she expressly did, that it made such a contribution. Ground 2: Mr Smith - asbestosis 144 In addressing ground 2, the appellant sought to identify two issues with particular reference to the case of Mr Smith. One was a challenge to the finding that he had asbestosis; the second challenged the proposition that there was no issue in relation to causation if the presence of asbestosis were established. 145 With respect to the first complaint, the precise legal error sought to be identified was unclear. The submission started with the concession that there was "a real conflict of opinion" as to whether Mr Smith suffered from asbestosis, an unpromising start in identifying an error of law. The substance of the complaint appears to have been that there was "no explanation" as to why the evidence of the witnesses for the appellant that he did not suffer from asbestosis was rejected. 146 So far as the diagnosis of having had asbestosis was concerned, her Honour dealt with that question in some detail from [203]-[233]. After setting out the evidence, including the conflicting opinions in some detail, her Honour concluded: "231 I prefer the evidence of Dr Jones to that of the defendant's experts on the issue of what the high resolution CT scans of Mr Smith's lungs showed, including the nature of the diseases of the lung suffered by him, given that Dr Jones is acknowledged as the pre-eminent radiologist in this field. His evidence is that asbestosis is the most common cause of UIP [usual interstitial pneumonia]. I accept the evidence of Mr Smith as to his exposure. 232 Therefore, accepting Dr Jones', which, together with that of Professor Breslin, who impressed me as an entirely independent witness, and also the evidence of Drs Burns, Barnes and Shilkin, leads me to find on the balance of probabilities that Mr Smith's UIP was asbestosis. The likely total cumulative exposure of Mr Smith was probably at least that estimated by Dr Francis. There is no issue that in the presence of asbestosis, lung cancer may be attributed to asbestos." 147 If the complaint is that her Honour gave no reasons for preferring the evidence of some experts over that of others, that is not so. Her Honour accepted Dr Jones as the "pre-eminent radiologist in this field" and accepted the evidence of Professor Breslin as "an entirely independent witness". These separate assessments provided a clear basis for preference, about which no complaint can be made on this appeal. 148 In relation to the second complaint, the relevant evidence needs to be viewed in context. The scientific context included the "precursor theory" accepted by some (though not the majority of the opinion called in the case) which held that the existence of asbestosis was a necessary precondition to the conclusion that lung cancer had been caused by inhalation of asbestos dust. To reject the precursor theory was not, however, to reject the proposition that the presence of asbestosis demonstrated a probability that asbestos had contributed to the lung cancer. In part, the significance of asbestosis was that it implied a relatively high level of exposure to asbestos dust, which might in turn justify the finding of a relative risk in excess of 2, being the basis of Professor Henderson's comments upon which the appellant sought to rely: Tcpt, 08/02/07, p 150 (35). 149 The appellant also sought to draw support from the evidence of its own witness, Dr Breslin, who accepted the statement that "the existence of asbestosis is not a necessary precursor or sign to enable attribution of a lung cancer to asbestos exposure": Tcpt, 09/02/07, p 214 (25). It is doubtful that his agreement to this statement, which contained two distinct propositions, indicated more than his rejection of the precursor theory. The appellant also sought to rely upon evidence given by Dr James Leigh describing the precursor theory as discredited because it hypothesized a mechanism for triggering cancer based on the existence of an "old scar", causing it to be known as the "old scar theory": Tcpt, 15/02/07, pp 413-414. Finally, the appellant's own expert, Professor Keith Shilkin stated in his report of 9 August 2005 (p 2.4): "Almost universally it is accepted that lung cancer may be attributed to asbestos exposure when asbestosis is present." 150 Her Honour was entitled to resolve any uncertainties and accept that evidence which was supportive of Mr Smith's case, including the categorical and unchallenged evidence of Professor Shilkin, as she did at [122]. No error in point of law has been made good. Ground 3: delay in delivering judgment 151 The third ground of appeal alleged that error could be "inferred" by reason of the long delay in delivering judgment, either as to "the totality of the judgment" or, in respect of "particular findings and legal rulings". On the basis that one needs to go to the written submissions to make sense the ground, no content was identified. Counsel stated that it would be "repetitive to make submissions on this issue". They noted that "maybe some of the errors made by the trial judge can be explained, although not excused, by the delay in delivery of judgment". 152 Whether it is appropriate for this Court to seek to find any substance in such a ground is doubtful. In truth the ground was misconceived and should have been abandoned. 153 The statement of legal principle upon which the appellant relied is that to be found in Hunt AJA in Monie v Commonwealth of Australia [2005] NSWCA 25; 63 NSWLR 729 at [43], where his Honour set out a number of propositions, many of which require elucidation. As explained by Giles JA in the same case at [3]: "The thrust of the approach is that extensive delay may cause an appellate court to take a more stringent approach in determining whether error has been demonstrated in the trial judge's findings or whether the trial judge's reasons are adequate." 154 Questions relating to the adequacy of reasons have been discussed above. Delay in delivering judgment may in some cases lead an appeal court to be reticent in accepting the benefits commonly attributed to the trial judge in assessing the evidence where the assessment has been long delayed. (Of course, whether it has in a particular case may not be revealed merely by the date of delivering judgment, or by the reasons.) Importantly, Monie was an appeal by way of rehearing under s 75A of the Supreme Court Act and thus an appeal in which challenges could be made to findings of fact. This was not such a case. Indeed, in the course of argument senior counsel for the appellant said (Tcpt, 16/11/09, p 21 (30)): "I think it is generally able to be said about this case that there [are] no relevant negative credibility findings anywhere. Some witnesses were shown a little preference over others but it was really determined on the basis that there were a number of intellectual issues raised by the particular experts." 155 That summary of the case should be accepted: it demonstrates the irrelevance of Monie. Ground 3 raised no challenge of substance and should also be rejected. Conclusions 156 The whole of the appellant's case was ultimately founded on the proposition that each of the workers died from a lung cancer, the cause of which could not be directly established, but which was likely to be, predominantly, cigarette smoking. 157 There were statements in the evidence which suggested that some of the experts misapprehended the questions asked of them or the issues before the Court. For example, Dr Leigh gave evidence which suggested ambivalence as to the distinction between a factor materially contributing to a condition and one materially contributing to the risk of the condition. However, there is no suggestion that her Honour fell into error in failing to draw that distinction. Secondly, there was evidence from Professor Berry which suggested that he thought that even where asbestos contributed to a condition, the condition could not be attributed to asbestos inhalation unless the contribution reached 50%. While her Honour did not make a numerical assessment of the contribution of asbestos to the lung cancers of any of the three workers, it is clear that she did not accept that the contribution exceeded 50%, nor did it need to do so to be "material". 158 There was ample evidence before her Honour to provide a basis for her conclusion that exposure to the inhalation of asbestos dust materially contributed to the lung cancers in each case. The appellant did not contend that either the definition of dust diseases, relevantly for this purpose "asbestos induced carcinoma", or the causation element required by s 8(1), was not established if asbestos made a material contribution, on the balance of probabilities, to the carcinomas. 159 Her Honour having made no error of law in construing the terms of s 8(1)(b), there was no decision in point of law by the District Court which was erroneous. To the extent that there could be an error of the relevant kind arising from the absence of evidence capable of supporting the conclusions reached, that basis of challenge was not made out. 160 Finally, to the extent that inadequacy of reasons can be a ground for identifying an erroneous award in point of law, the substance of that ground was also not made out. 161 The appeals in respect of the decisions of the District Court in relation to each of the three respondents should be dismissed. The appellant should pay the respondents' costs of the appeals. 162 HANDLEY AJA: In these matters I have had the great benefit of reading the reasons for judgment of Basten JA in draft. He has thoroughly reviewed the submissions of the appellant, the relevant evidence, and the applicable legal principles. I agree that the appellant failed to establish that it is aggrieved by an award of the District Court "in point of law or on a question as to the admission or rejection of evidence" (District Court Act s 142N(1)), not because it was not aggrieved but because it failed to establish any relevant error within the section. 163 For that reason the appeals fail and should be dismissed. I agree generally with His Honour's reasons for reaching that conclusion. However I express no view on statements by His Honour which are not necessary for the decisions in these appeals. ********** DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. 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