Allianz Australia Ltd v Sim; WorkCover Authority (NSW) v Sim; Wallaby Grip (BAE) Pty Ltd (In liq) v Sim [2012] NSWCA 68

Lorraine Fay Sim v Allianz Australia Limited [2010] NSWDDT 19 – trial decision

Prof Henderson’s evidence on cancers

Further to earlier postings in relation to causation in asbestos-related disease claims, especially lung cancer.

I refer you to the headnote in the first instance and in particular, the use of expert evidence, principally Prof Henderson, in establishing causation in multi-party asbestos-related lung cancer claims. Notably, the NSW Court of Appeal (Basten JA, Allsop P and Meagher JA agreeing) did not interfere with the causation rationale and helpfully went to some trouble to explain the law in this area [133 -145]. Appreciably, the causation test is not contained in the analogue Civil Liability Acts or the Workers’ Compensation and Rehabilitation Act. It’s a reminder for dust-related conditions like asbestos that the common law applied. The rules in Bonnington Castings Ltd v Wardlaw [1956] UKHL 1; [1956] AC 613 and March v E & MH Stramare Pty Ltd [1991] HCA 12; 171 CLR 506 at 515-516 (Mason CJ), remain. It is also essential in the distinction in liability between an indivisible disease, such as lung cancer and mesothelioma, as opposed to a divisible disease, like asbestosis and asbestos-related pleural disease. Importantly, the court found the “but for” test did not need to apply in this instance.


[This headnote is not to be read as part of the judgment]

Mr Sim worked with asbestos for many years and in the employ of various employers. He contracted asbestosis and subsequently lung cancer. He died on 6 July 2009. Mrs Sim (“the plaintiff”), the legal personal representative of his estate, commenced proceedings in the Dust Diseases Tribunal (“the Tribunal”) against four of these employers or their insurers. The WorkCover Authority of NSW (“WorkCover”) incurred
liability on behalf of the defunct insurer of the second and third employers.

The Tribunal admitted expert evidence from Professor Henderson, Associate Professor Bryant and Dr Yates. The evidence asserted that it could not be established that the tortious exposure during employment with each employer was a necessary causal element in the chain of events leading to the lung cancer. The Tribunal accepted this evidence. Nevertheless, the Tribunal held that the employers’ negligence had caused Mr Sim’s lung cancer.

The Tribunal:

(a) found that the appellants were jointly and severally liable in respect of Mr Sim’s lung cancer and awarded damages of $317,561.85,

(b) found that WorkCover was liable in respect of the second employer pursuant to the Workers Compensation Act 1987 (NSW), s 151AB, and

(c) ordered that WorkCover pay the plaintiff’s costs on an indemnity basis from 14 May 2010, following an offer of compromise which was not accepted by WorkCover.

The issues for determination on appeal were:

(i) whether the Tribunal erred in admitting the expert evidence because the opinions of the experts were not “wholly or substantially based” on their “training, study or experience”,

(ii) whether each of the four employers was implicated or whether all could escape because it could not be established that the tortious exposure during employment with each was a necessary causal element in the chain of events,

(iii) whether the Tribunal erred in drawing an adverse inference from the appellants’ failure to call expert medical evidence on the question of causation,

(iv) whether the Tribunal erred in finding that WorkCover was liable in respect of the second employer pursuant to the Workers Compensation Act 1987 (NSW), s 151AB, and

(v) whether the Tribunal erred in ordering that WorkCover pay the plaintiff’s costs on an indemnity basis from 14 May 2010.

The Court held, dismissing the appeal:

In relation to (i)

(per Basten JA, Allsop P and Meagher JA agreeing)

1. It is appropriate to look at all of the evidence to see whether, by the end of the trial, any error in admitting the written reports of the experts had been overcome by subsequent evidence: [67]

2. The cumulative theory of causation was in issue, about which an expert could helpfully opine. The challenge to the admissibility of the expert evidence must be rejected: [116]-[122]

Clark v Ryan [1960] HCA 42; 103 CLR 486 distinguished.

(per Allsop P, Meagher JA agreeing)

3. Professor Henderson’s evidence was not inadmissible to prove the causal relationship between the exposures and the lung cancer. His evidence drew upon his specialised knowledge. The material crosses the line at which lay analysis can discern any inadequacy of the requirements of Evidence Act 1995 (NSW), s 79: [26]-[28]

Dasreef v Hawchar [2011] HCA 21; 243 CLR 588 applied.

4. Professor Henderson rationally explained his opinion by reference to facts, assumptions and specialised knowledge, and was not expressing an opinion about heightened risk: [31]

Bendix Mintex Pty Ltd v Barnes (1997) 42 NSWLR 307; Evans v Queanbeyan City Council [2011] NSWCA 230 distinguished.

5. As Professor Henderson is a pathologist, if he otherwise has the basis to express an opinion, he is concerned with the science of the causes and effects of diseases: [34]

Amaca Pty Ltd v King [2011] VSCA 447 approved; Amaca Pty Ltd (under NSW administered winding up) v Booth [2011] HCA 53; 86 ALJR 172 applied.

In relation to (ii)

(per Basten JA, Allsop P and Meagher JA agreeing)

6. Increase in risk is not to be equated with factual causation: [98]

Amaca Pty Ltd (under NSW administered winding up) v Booth [2011] HCA 53; 86 ALJR 172 applied.

7. In circumstances in which the negligence of each defendant was insufficient to effect the damage, but the combined force of two was sufficient, each should be held liable in respect of an indivisible outcome: [139]-[140], [145]

Bonnington Castings Ltd v Wardlaw [1956] UKHL 1; [1956] AC 613 applied; March v E & MH Stramare Pty Ltd [1991] HCA 12; 171 CLR 506; Amaca Pty Ltd v Ellis [2010] HCA 5; 240 CLR 111; Amaca Pty Ltd (under NSW administered winding up) v Booth [2011] HCA 53; 86 ALJR 172 discussed.

(per Allsop P, Meagher JA agreeing)

8. Under general law principles, the counterfactual satisfaction of the but for test is not essential: [49]

March v E & MH Stramare Pty Ltd [1991] HCA 12; 171 CLR 506; Amaca Pty Ltd (under NSW administered winding up) v Booth [2011] HCA 53; 86 ALJR 172; Strong v Woolworths Ltd [2012] HCA 5 applied.

In relation to (iii)

(per Basten JA, Allsop P and Meagher JA agreeing)

9. No error of law was demonstrated in the manner in which the Tribunal dealt with the failure of the appellants to adduce expert evidence: [126], [128]

In relation to (iv)

(per Basten JA, Allsop P and Meagher JA agreeing)

10. There does not appear to have been any issue raised before the Tribunal that the date of Mr Sim’s employment with the second employer extended past the date of expiration of the relevant insurance policy, nor was it suggested that the insurance policy terminated before the date of sale of the business: [163]

In relation to (v)

(per Basten JA, Allsop P and Meagher JA agreeing)

11. It may be that the provisions of the Dust Diseases Tribunal Regulation 2007 (NSW), Pt 6, only operate to the extent that they are not inconsistent with the equivalent provisions in the Uniform Civil Procedure Rules: [168]

12. No error of law was shown in the Tribunal’s conclusion that the plaintiff made a valid offer of compromise and was entitled to indemnity costs: [173], [175], [180]


Science may struggle to give complete expressions of reasons for pathology and aetiology of disease. Still more is it likely to struggle to express opinions about what might have happened had an indefinable or imprecise body of facts not occurred. For the law to demand that exercise in the working out of responsibility for the consequences of tortious wrongdoing would be to demand unreality. As Dixon J said in Adelaide Stevedoring Co Ltd v Forst [1940] HCA 45; 64 CLR 538 at 569, cited by Gummow J, Hayne J and Crennan J in Amaca v Booth (at 479-480 [69]):

“I think that upon a question of fact of a medical or scientific description a court can only say that the burden of proof has not been discharged where, upon the evidence, it appears that the present state of knowledge does not admit of an affirmative answer and that competent and trustworthy expert opinion regards an affirmative answer as lacking justification, either as a probable inference or as an accepted hypothesis.”


The requirement for such counterfactual satisfaction of the but for test was one of the matters that Mason CJ rejected in March v Stramare, that Gummow J, Hayne J and Crennan J can be taken to have rejected in Amaca v Booth at [70] and that French CJ, Gummow J, Crennan J and Bell J rejected in Strong v Woolworths at [26]-[28].


The first step in the argument is undoubtedly correct: increase in risk is not to be equated with factual causation. As noted by French CJ in Amaca Pty Ltd (under NSW administered winding up) v Booth [2011] HCA 53; 86 ALJR 172 at [41]:

“Causation in tort is not established merely because the allegedly tortious act or omission increased a risk of injury. The risk of an occurrence and the cause of the occurrence are quite different things.”


As his Honour further noted, assessment of the risk of an occurrence is “prospective in character”: at [42]. Further, the reasoning continued at [43]:

“An after-the-event inference of causal connection may be reached on the civil standard of proof, namely, balance of probabilities, notwithstanding that the statistical correlation between the first event and the second event indicated, prospectively, no more than a ‘mere possibility’ or ‘real chance’ that the second event would occur given the first event.”


In Amaca v Booth, the question was whether Mr Booth had established that his malignant pleural mesothelioma was caused by his exposure to asbestos in working on brake linings over a period of 30 years, and involving two separate defendants. After noting the distinction between a predictive assessment of risk and a retrospective assessment of causation, French CJ stated at [43]:

“The existence of an association or a positive statistical correlation between the occurrence of one event and the subsequent occurrence of another may be expressed as a possibility, which may be no greater than a ‘real chance’ that, if the first event occurs, the second event will also occur. The mere existence of such an association or correlation does not justify a statement, relevant to factual causation in law, that the first event ‘creates’ or ‘gives rise to’ or ‘increases’ the probability that the second event will occur. Such a statement contains an assumption that if the second event occurs it will have some causal connection to the first. However, if the association between two events is shown to have a causal explanation, then the conclusion may be open, if the second event should occur, that the first event has been at least a contributing cause of that occurrence.”


His Honour then referred to the nine factors identified by Sir Austin Bradford-Hill as matters having the character of circumstantial evidence of a casual relationship: at [44]. These factors had been referred to by Professor Henderson in Amaca, and in his report in the present case. Significantly however, the Chief Justice pointed to the distinction between a finding that conduct has increased the risk of injury and a mere statistical correlation between such conduct and such injuries. The former involves, inherently, a causal connection, which the latter need not: at [49]. His Honour concluded at [51]:

“It is enough for present purposes to say that an inference of factual causation, as against both Amaca and Amaba, was open on the evidence before the primary judge. The cumulative effect mechanism involving all asbestos exposure in causal contribution to the ultimate development of a mesothelioma had been propounded and was accepted by his Honour. It depended upon an understanding of physiological mechanisms. It did not depend upon the epidemiology.”


The joint judgment of Gummow, Hayne and Crennan JJ reached a similar conclusion. After noting the significance of the “single fibre” theory in the development of the law in England, their Honours noted the contrary view, based on multiple exposures, as explained by Professor Henderson in that case: at [79]. Subject to an attack not made in the present case, their Honours set out and accepted the plaintiff’s argument in Amaca v Booth in the following terms at [83]:

“Mr Booth developed his case in the following steps: (1) he had contracted mesothelioma; (2) the only known cause of that disease is exposure to asbestos; (3) the expert evidence at trial, accepted by the primary judge, was that: (a) exposure to asbestos contributes to the disease; and (b) the prospective risk of contracting the disease increases with the period of significant exposure; (4) Mr Booth had two periods of significant exposure; (5) it is more probable than not that each period of exposure made a material contribution to bodily processes which progressed to the development of the disease.”


Common ground 1(f) asserted that it was not reasonably open on the admissible evidence to conclude that Mr Sim “would not have contracted lung cancer but for the negligence of” each appellant.


The premise underlying this ground was that the conduct of each appellant must be a sine qua non with respect to the harm suffered. This is sometimes described as the “counterfactual test” of causation because it poses the hypothetical question as to whether the harm would have resulted, if the defendant’s tortious conduct were removed from the equation: see, eg, Michael S Moore, Causation and Responsibility (OUP, 2010), p 84. It is also known as the “necessary condition” test, in which form it has been adopted in one part of s 5D of the Civil Liability Act 2002 (NSW). Its operation in that context does not arise in the present case, to which the Act does not apply: see s 3B.


The second proposition relied on by the appellants was that the “commonsense” approach to causation, long favoured by the common law and approved in March v E & MH Stramare Pty Ltd [1991] HCA 12; 171 CLR 506 at 515-516 (Mason CJ), should be abjured in circumstances where causation is not capable of commonsense assessment and can only be established by application of scientific principles. For these purposes, the appellants did not seek to set up a necessary condition test as the only relevant test; they accepted that the results of applying that test may be over-inclusive, so that legal policy may restrict the category of those liable, even where the conduct is a necessary condition of the harm suffered. On the other hand, they said that satisfaction of the necessary condition test is a necessary condition of liability.


This approach is too limited and does not reflect presently accepted general law principles. In its terms, it rejects reliance on “material contribution” as a sufficient causal connection. In a classic analysis of causation principles in the law of tort entitled “Causation in Tort Law” (1985) 73 Cal L Rev 1735, Professor Richard W Wright undertook a comprehensive survey of causation in tort law, the analysis covering theories from David Hume to the date of publication. In discussing the ‘NESS test’ (necessary elements of a sufficient set of conditions) as articulated by Hart and Honoré, Wright noted that the courts had not required independent sufficiency for each element in cases of duplicative causation: pp 1791-1792. Referring to two early American cases, Corey v Havener, 182 Mass 250; 65 NE 69 (1902) (noisy motorcycles) and Anderson v Minneapolis, St P & S Ste M Ry, 146 Minn 430; 179 NW 45 (1920) (merged fires) he noted that the courts did not require the plaintiff in either case to prove independent sufficiency of each contributing factor, but only that each factor contributed to the injury. Professor Wright noted similar results in pollution cases including, more recently, Michie v Great Lakes Steel Div, [1974] USCA6 248; 495 F2d 213 (6th Cir), cert denied, 419 US 997 (1974).


This analysis is apt in the present case: to oversimplify the facts for the purposes of noting the principle, one may assume there were four defendants each of whom contributed (through tortious conduct) 20% of the exposure to asbestos dust which caused the plaintiff’s lung cancer; that the contribution of each, taken alone, would not have been shown, on the balance of probabilities, to cause the lung cancer, but that the combination of any two would have been sufficient. Thus the contribution of each individually was neither necessary (because there were three other equivalent contributions) nor sufficient to cause the injury. The example was illustrated in the course of argument by a temporal analysis. Assuming two were sufficient, if the first two in point of time had the necessary effect, the third and fourth would have been redundant; alternatively, if the third and fourth were sufficient, it could not be demonstrated on the balance of probabilities that the chain of causation commenced with either the first or second defendant.


The appellants contended that if each defendant should in those circumstances be found liable, the conclusion reflected the need, identified in Fairchild, to vary the general law principles, even those relating to material contribution, for the defendants, or any of them, to be found liable. It not being appropriate for the Tribunal, nor for that matter this Court, to create a new form of tortious liability, the appellants contended that they should succeed: cf Tabet v Gett [2010] HCA 12; 240 CLR 537; Gett v Tabet[2009] NSWCA 76; 254 ALR 504. However, the flaw in the appellants’ argument is its foundation in epidemiology. If Professor Henderson’s evidence was inadmissible, the appellants succeed on a different basis; if Professor Henderson’s evidence was admissible (as held above) then it must be taken into account in the analysis of causation. Indeed, as explained by Lord Phillips PSC in Sienkiewicz v Greif (UK) Ltd[2011] UKSC 10; [2011] 2 WLR 523 at [90]:

“I see no scope for the application of the ‘doubles the risk’ test in cases where two agents have operated cumulatively and simultaneously in causing the onset of a disease. In such a case the rule in Bonnington [discussed below] applies. Where the disease is indivisible, such as lung cancer, a defendant who has tortiously contributed to the cause of the disease will be liable in full. Where the disease is divisible, such as asbestosis, the tortfeasor will be liable in respect of the share of the disease for which he is responsible.”


In the 2009 publication of the American Law Institute (ALI), Restatement (Third) of Torts: Liability for Physical and Emotional Harm, Vol 1 380-1 (s27, Illustration 3) an example is given of three people who independently but simultaneously and negligently lean against the plaintiff’s car, causing it to roll over the edge of a precipice. On the hypothesis presented, the force applied by each was insufficient to effect the damage, but the combined force of two was sufficient. Accordingly, the conduct of none was necessary or sufficient to cause the damage. This constituted one of a number of examples given by Professor Jane Stapleton in “Factual Causation” (2010) Fed L Rev 467 at 475-476. Approving the statement of the ALI, Professor Stapleton accepts that each should be held liable in respect of an indivisible outcome.


There is authority in this country to support that approach. Thus, the doctrine of material contribution was applied by the House of Lords in Bonnington Castings Ltd v Wardlaw [1956] UKHL 1; [1956] AC 613, a case involving “pneumoconiosis … caused by a gradual accumulation in the lungs of minute particles of silica inhaled over a period of years”: at 621 (Lord Reid). There were two sources of the dust inhaled by the plaintiff, namely pneumatic hammers and swing grinders. It was conceded by the employer that the dust from the swing grinders should have been intercepted and removed. Lord Reid stated at 621:

“… I cannot agree that the question is: which was the most probable source of the respondent’s disease, the dust from the pneumatic hammers or the dust from the swing grinders? It appears to me that the source of his disease was the dust from both sources, and the real question is whether the dust from the swing grinders materially contributed to the disease. What is a material contribution must be a question of degree. A contribution which comes within the exception de minimus non curat lex is not material, but I think that any contribution which does not fall within that exception must be material.”

Viscount Simons (at 618), Lord Tucker (at 623), Lord Keith of Avonholm (at 626) and Lord Somervell of Harrow (at 627) agreed.


In March v Stramare, Mason CJ (with the concurrence of Deane J, writing separately, Toohey and Gaudron JJ) noted that uniformity of approach to questions of causation might not be possible, given the purpose of allocating legal responsibility for conduct. Bonnington Castings (at 620) was referred to as providing support for the following proposition (at 514):

“Nonetheless, the law’s recognition that concurrent or successive tortious acts may each amount to a cause of the injuries sustained by a plaintiff is reflected in the proposition that it is for the plaintiff to establish that his or her injuries are ’caused or materially contributed to’ by the defendant’s wrongful conduct.”


More recently, the statement of Lord Reid in respect of material contribution was referred to without disapproval by the High Court in Amaca v Ellis [2010] HCA 5; 240 CLR 111. Their Honours stated:

“[67] It is important to recognise the context in which this statement was made. The issue in Bonnington Castings was whether exposure to silica dust from poorly maintained equipment caused or contributed to the pursuer’s pneumoconiosis, when other (and much larger) quantities of silica dust were produced by other activities at the pursuer’s workplace. Those other activities were conducted without breach of duty. As Lord Reid rightly pointed out, the question in the case was not what was the most probable source of the pursuer’s disease: dust from one source or the other. The question was whether dust from the poorly maintained equipment was a cause of his disease when the medical evidence was that pneumoconiosis is caused by a gradual accumulation of silica particles inhaled over a period of years.

[68] This description of the issue of causation in Bonnington Castings shows how different it is from the issue of causation in this case. The issue in Bonnington Castings was whether one source of an injurious substance contributed to a gradual accumulation of dust that resulted in disease. The issue here is whether one substance that can cause injury did cause injury. Or, to adopt and adapt what Starke J said in Adelaide Stevedoring Co Ltd v Forst, was Mr Cotton’s cancer ‘intimately connected with and contributed to’ by his exposure to asbestos? Questions of material contribution arise only if a connection between Mr Cotton’s inhaling asbestos and his developing cancer was established. Knowing that inhaling asbestos can cause cancer does not entail that in this case it probably did. For the reasons given earlier, that inference was not to be drawn in this case. Questions of what is a material contribution do not arise.”


While questions of material contribution did not arise in that case, there was no suggestion that, in another case, they could not support a finding of liability: indeed the discussion assumes that they could. Further, in terms of the precise question identified at [68], it was not in dispute in the present case that asbestos did cause Mr Sim’s lung cancer: the question related rather to what has been described as “the defendant-identification issue”: Stapleton, “Factual Causation and Asbestos Cancers”, (2010) 126 LQR 351 at 356.


In Amaca v Booth, Gummow, Hayne and Crennan JJ referred to the same issue at [70]:

“The ‘but for’ criterion of causation proved to be troublesome in various situations in which multiple acts or events led to the plaintiff’s injury, for example, where the development of a particular medical condition was the result of multiple conjunctive causal factors. In such cases what may be unclear is the extent to which one of these conjunctive causal factors contributed to that state of affairs. These situations have been addressed by the proposition stated by Lord Watson in Wakelin v London and South Western Railway Co [(1886) 12 App Cas 41 at 47] that it is sufficient that the plaintiff prove that the negligence of the defendant ’caused or materially contributed to the injury’.”

Their Honours also referred to the speech of Lord Reid in Bonnington Castings at 621 and Amaca v Ellis at [67].


The appellants identified no authority for the proposition that substantial successive and cumulative tortious conduct, independently engaged in by several defendants, did not render each liable for the consequential and individual harm, in circumstances where individually, the tortious conduct was neither necessary nor sufficient to cause the harm. The line of authorities referred to above demonstrates that evidence of causation satisfying those conditions is sufficient to establish liability according to general law principles. Accordingly, ground 1(f) must be rejected.

Brisbane Barrister – David Cormack


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