Amaca Pty Ltd v Ellis

Amaca Pty Ltd v Ellis; The State of South Australia v Ellis; Millennium Inorganic Chemicals Ltd v Ellis [2010] HCA 5 (3 March 2010)

Summary

Majority: French CJ, Gummow, Hayne, Heydon, Crennan, Kiefel and Bell JJ

Decision: Appeal allowed.

The respondent died of lung cancer. He was a smoker and exposed to asbestos in the course of his employment. No definitive cause of the respondent’s lung cancer was determined (scientifically or medically). The Court found that it could not be established that it was more probable than not that the asbestos was the cause of the respondent's lung cancer; ‘because no more was established than that, although exposure to asbestos may have been a cause of his cancer, it was not a probable cause.’ (at [14]). Accordingly, causation was not made out and therefore the claim must fail.

Facts

The respondent Paul Steven Cotton died from lung cancer in 2002. He had smoked on average 15 to 20 cigarettes a day for more than 26 years before he was diagnosed with lung cancer. In the employ of the Engineering and Water Supply Department of the State of South Australia (1975-1978) and then Millennium Inorganic Chemicals Ltd (1990-2002), the respondent was exposed to ‘respirable asbestos fibres’. The existence of duty and breach were not in issue. The principle issue was causation; “but for” the respondent’s exposure to asbestos would he have contracted lung cancer? The respondent sought to establish that asbestos caused or contributed to the lung cancer.

Epidemiological evidence

At trial epidemiological evidence was put forward by four experts with extensive expertise in asbestos related diseases. The evidence of each collectively was that ‘many sufferers of lung cancer had smoked tobacco, a few had been exposed to asbestos; some of those who had been exposed to asbestos had also smoked; some had been neither smokers nor exposed to asbestos.’ (at [20]) Calculation of the risk involved the formulation of ‘relative risk’: the differentiation between the risk of the suffering from the disease if exposed to smoking, asbestos or both, in contrast to those not exposed to these risk factors. The evidence before the Court in first instance was that in addition to smoking and asbestos having a measurable risk factor of contracting lung cancer, both smoking and asbestos exposure together has ‘a synergistic effect’: being that the risk of lung cancer from smoking and exposure to asbestos is greater than the addition of the risk of smoking to the risk associated with asbestos exposure. (at [21])

While there were differences between each of the experts as to the exact quantifiable probable cause of the respondents cancer, collectively they provided that the risk of lung cancer was far greater from smoking than from exposure to lung cancer [asbestos]. None of the four witnesses discerned the probability that the respondent’s cancer was caused by asbestos exposure to be greater than 23% irrespective of his smoking. Each gave a figure of 67% or greater that the respondent’s cancer was a result of his smoking alone. (at [30])

Decision

The Court found that the respondent’s exposure to asbestos which may have caused his cancer was insufficient to satisfy that the exposure more probably than not was the causative factor in his lung cancer. The respondent’s assertion that smoking and asbestos exposure ‘must work together’ was unsupported by the expert evidence given at trial.

It may be accepted (at least for the purposes of debate) that the synergistic or multiplicative effect suggests that in some cases the two carcinogens will have contributed to the development of an individual patient's cancer. But the proposition which the plaintiff advanced was an absolute proposition of universal application: smoking and asbestos must work together and they must have worked together in this case. That proposition was not established. (at [54])

The respondent’s dissection of the possible cause of his lung cancer as either solely smoking or the synthesis of smoking and asbestos to the exclusion of other possible causes, could not be accepted. While such a dissection resulted from epidemiological evidence that most people who contract lung cancer were smokers and the second highest incidence of lung cancer resulted from both a culmination of smoking and exposure to asbestos, does not reduce the cause of lung cancer to two definitive causal explanations. Without further evidence, there is insufficient basis to establish a causal connection between the respondent’s asbestos exposure and his lung cancer. The respondent's reliance on the evidence that smoking and exposure to asbestos is more dangerous than either in isolation is insufficient to establish causation. (at [55-57])

The categorisation by the respondent of smoking and asbestos as ‘most dangerous’ - in the sense that asbestos was more likely to be the cause of the cancer - was not supported by the evidence. Of the expert witnesses, none measured the likelihood of the cancer being caused by asbestos (solely or in combination with smoking) to be greater than 23%. The likelihood of smoking being the sole cause was high, up to 92%. Therefore the ‘quantitative comparison of risk’ of smoking in combination with asbestos as ‘most dangerous’ was not supported by the evidence. (at [59]) It is more probable than not that smoking was the cause of the respondent’s cancer. Furthermore exposure to asbestos, whether alone or in conjunction with smoking was low and fails to satisfy that it is more probable than not that the respondent’s cancer was caused by asbestos exposure. (at [64])

Commentary

Ellis provides an example where the prevailing test for causation, provides for what may be viewed as an unfavourable outcome. In this case, duty and breach were not in contention. However, due to the complicated and inconclusive nature of the medical and scientific knowledge in the area, a casual relationship could not be established. It would appear that Epidemiological evidence is difficult even unlikely, on its own, to be sufficient to establish causation.

Ellis emphasises the difficulty in establishing causation in circumstances where the damage was the result of 2 or more independent possible sources each capable of resulting in the damage independently. Similar difficulty ensues where the damage was the result of two or more separate causes which act synergistically. This poses the question of whether the test of causation should be lowered. This is a complicated issue, which I will not endeavour to tackle here. It is worthwhile however to note that this case is likely to encourage discussion.

The Court did not appear to be interested in reassessing causation in Ellis. Admittedly the question was not asked, but the Court gave no inclination in their joint judgement that they would consider a reassessment. Their Honours concluded with a brief justification of an apparent paradox in their decision. The fact that the Court felt the need/desire to do so is interesting as is their explanation itself. I have therefore reproduced it here (at [69-70]):

A paradoxical result?

It was submitted that the conclusion that causation was not established in this case entailed a paradox. If consideration of the results of the population studies described in evidence in this matter does not permit the inference that Mr Cotton's cancer was caused or contributed to by exposure to asbestos, no claim by an individual in Mr Cotton's position could succeed. And yet, the argument continued, the population studies showed that exposure to asbestos was a cause of cancer in some cases. How then could it be right to reach a result that entailed the corollary that all individual claims would fail?

The answer to the question can be expressed in several different ways. All depend upon the basic and unpalatable fact that no scientific or medical examination can now say, with certainty, what caused Mr Cotton's cancer or lung cancer in any other particular case. As explained at the outset of these reasons, despite this uncertainty, the courts must, and do, "reduce to legal certainty [a question] to which no other conclusive answer can be given". The courts do that by asking whether it is more probable than not that X was a cause of Y. Saying only that exposure to asbestos may have been a cause of Mr Cotton's cancer is not a sufficient basis for attributing legal responsibility. Observing that a small percentage of cases of cancer were probably caused by exposure to asbestos does not identify whether an individual is one of that group. And given the small size of the percentage, the observation does not, without more, support the drawing of an inference in a particular case. The paradox, if there be one, arises from the limits of knowledge about what causes cancer.