On 3 March 2010 the High Court of Australia delivered a very important decision relevant to causation in lung cancer cases. The decision has broader application to other types of injury in which the precise pathogenesis of the illness is, as a matter of medical science, uncertain and where there is more than one potentially causative element.
The case also considered the question of causation in circumstances where there had been successive breaches of duties by tortfeasors.
Mr Cotton died of lung cancer. He was a smoker and it was well established that smoking can cause lung cancer. He consumed between 15 and 20 cigarettes per day for about 26 years. He was exposed to respirable asbestos fibres in the course of two successive employments, first with the Engineering Water Supply of the State of South Australia and later by Millennium. His exposure to asbestos when working for the State was from asbestos cement pipes manufactured by Amaca.
His executrix, Ms Ellis, maintained proceedings against the State, Millennium and Amaca alleging that the asbestos exposure was a cause of the lung cancer.
The claim succeeded at trial and, by majority, before the Full Court of the Supreme Court of Western Australia. Special leave was granted to the State, Millennium and Amaca to appeal to the High Court of Australia.
Questions of foreseeability and consequently breach of duty were originally argued and lost by the defendants. The sole issue for consideration by the High Court was causation.
Medical and scientific evidence
It was not controversial that:
- Smoking can cause lung cancer
- Breathing in asbestos fibres can also cause lung cancer
- Smoking in some combination with breathing in asbestos fibres (via a process not current understood by medical science) can increase the risk of developing lung cancer
- Those activities do not inevitably result in lung cancer so it is not inevitable that a person who smokes, or breathes in asbestos fibres, or smokes and breathes in asbestos fibres, will develop lung cancer
- Lung cancer develops in some people who have not smoked nor inhaled asbestos fibres.
No expert evidence was available to say definitively what caused Mr Cotton's cancer. The only evidence was that arising from epidemiological studies. Epidemiology is the study of disease progression through population and is, in general terms, a complex analysis of data leading to conclusions by expert epidemiologists as to the increase in risk of a particular activity (such as smoking) being the cause of an illness (say lung cancer) by comparison to another activity being a cause.
In Ellis, although differing depending upon the assumptions as to the quantity and timing of asbestos exposure by comparison to the quantity and timing of smoking, the experts unanimously concluded that it was substantially more likely that Mr Cotton's lung cancer arose from smoking rather than smoking in some combination with inhaling asbestos fibres rather than from inhaling asbestos fibres alone.
The high point of the plaintiff's evidence was that, on a risk analysis, smoking alone was 67% likely to be the cause of the cancer whereas asbestos alone or in combination with smoking was at most 23% likely to have been the cause (the balance of risk, 10%, on that scenario, attributed the cancer to factors other that smoking or asbestos).
Decision of the High Court
The High Court disagreed with the approach taken by the majority in the Court of Appeal and the Trial Judge in assessing causation by reference to the cumulative asbestos exposure over the successive employment periods. Rather the Court held the appropriate analysis was to consider whether the individual breach of duty was, in itself, causative of the damage.
Although it was unnecessary in this case (because of the conclusion reached on causation generally) for the Court to consider an 'apportionment' of the risk between employment periods it follows that a claimant will be required to establish that the particular exposure arising from each successive breach by a tortfeasor was in itself sufficient to satisfy the causation test.
On the question of causation the High Court held that it is insufficient to show that the inhalation of asbestos fibres merely increased the risk (or 'may have' caused) the cancer. Rather it is necessary to show that the asbestos exposure was actually a cause of the lung cancer in the individual bringing the claim. That is a matter of fact which requires proof on the balance of probabilities that it was more probable than not that the negligence of each defendant was a cause of, in this case, Mr Cotton's cancer.
It is clear from the judgment that an epidemiological conclusion that asbestos had a 23% chance of having been involved in the development of the lung cancer does not 'tip' the balance of probabilities.
Of particular assistance the High Court explained the relevance of 'material contribution', often argued by claimants in this type of case by distinguishing it on the question it analysed. Material contribution was said by the High Court to be relevant only after proof of causation. That is, in a case based on epidemiological risks, it is necessary to show that the risk of the injury being caused by, say asbestos, has 'come home' before considering whether the specific exposures to asbestos amongst successive tortfeasors made a material cause to the asbestos related injury.
The decision is of significant assistance to parties dealing with the question of causation in cases involving injury of uncertain pathogenesis. The issue to be considered is in circumstances where one substance 'can' cause an injury causation will only be established if it is shown that in the plaintiff's case it 'did' cause the injury assessed on a balance of probability standard.
The decision of the High Court is consistent with the approach followed by the NSW Court of Appeal in Seltsam v McGuiness in which Speigalman CJ held that in order to establish causation on a 'risk analysis' it was necessary to establish that the exposure to the relevant substance (in that case asbestos fibres) at least approached doubling the risk of the plaintiff developing the illness by comparison to the risk presented had the claimant not been exposed to that substance.
The decision will result in significant focus being given to the facts of exposure to the various carcinogens and, absent developments in medical science, is likely to present significant difficulty for a number of sufferers of lung cancer in succeeding in establishing causation and thus an entitlement to damages.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.