Vines, Prue --- "Editorial: Insights into the complexities of causation" [2020] PrecedentAULA 12; (2020) 157 Precedent 2

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EDITORIAL: INSIGHTS INTO THE COMPLEXITIES OF CAUSATION

By Professor Prue Vines

Proving causation is often difficult. Causation in law has commonly been divided into factual and normative parts, although views about the limits of the division have differed – classically, the division has been encompassed by some form of the ‘but for’ and ‘scope of liability’ tests. The ‘commonsense causation’ established in March v Stramare (E & MH) Pty Ltd,^[1] which attempted to bring together factual cause and norms, is now the only test that is used where the Civil Liability Act (CLA) regimes do not apply. The various CLAs have their own formulation, as do other statutory regimes such as the Corporations Act 2001 (Cth) and the Australian Consumer Law.

Both the factual and normative parts of the causation decision give rise to difficulties, some of which are considered in this edition. Factual causation raises difficulties where omissions are at issue and where there are multiple possible causes and the court seeks only one. This is sometimes dealt with by accepting a material contribution or ‘a factor’ test. Reliance on epidemiological or statistical evidence can be problematic because it seeks to apply population evidence to individuals, sometimes without evidence to prove which sub-population the individual might fit into. This is illustrated in cases involving dust diseases, loss of chance and medical causation. If factual causation is established (and sometimes if it isn’t) the court may attempt to deal with the issue through a normative approach, including the use of statutory interpretation or reference to public policy considerations.

Elise Bant maps out these tests in her article. She considers the situation where a plaintiff purchases shares at under value because the company fails to disclose (omits) a salient fact to the market. When the market finds out, it corrects itself and the plaintiff may lose out. When it is clear that factual causation is established, should the plaintiff be compensated? How does the court use statutory interpretation to determine whether reliance is relevant or how much the plaintiff knew? Simon Gibbs observes that in Australia, reliance has been rejected as a necessary requirement for market-based causation where an investor does not know or does not care about relevant information. This means that merely transacting in an uninformed market can satisfy the statutory test in a continuous disclosure case under the Corporations Act.

Some of the difficulties created by proving causation of psychiatric injury are addressed by Alex Collie. Proof is particularly difficult where multiple traumatic events or stressors can be identified, such as where children have been abused in institutions and have subsequently suffered further trauma. Similarly, as Abhi Mukherjee discusses, where a psychiatric injury is suffered in the context of exposure to trauma at work, courts may encounter difficulties in identifying the particular breach of duty by the employer, which in turn complicates the causation issue. Multiple possible causes also feature in many dust disease cases, as Martin Rogalski explores, and both he and Duncan Graham (discussing medical negligence and the use of epidemiological evidence) show how the particular configuration of exposure and disease creates complex problems of proof. Where there are multiple exposures or competing causes, it has often been held that there is no evidence that one cause is more likely than another, particularly if the harm is asbestosis and a threshold level of accumulation is not found. On the other hand, the High Court has held that any exposure to asbestos might be deemed a cause of mesothelioma.^[2]

The problem of hindsight bias is particularly difficult in failure to warn cases because of the natural human assumption that, for example, if a person had been warned of the risks of undertaking a medical procedure they would not have gone ahead with the procedure. This has been dealt with by special provisions in the CLA regimes (for example, s5D(3)(b) of the NSW Act). Richard Douglas shows that this provision, despite its appearance, may not be a complete barrier to the introduction of evidence supporting the causal link.

Causation is central to many causes of action, and even where it is not, if damages are sought, causation must be established. The articles in this edition make a valuable contribution by teasing out the complex causation problems which practitioners confront.

Professor Prue Vines is Associate Dean (Education) and Co-Director of the Private Law Research and Policy Group at UNSW Law. EMAIL [e-mail].

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^[1] [1991] HCA 12; (1991) 171 CLR 506.

^[2] Amaca Pty Ltd v Booth [2011] HCA 53; (2011) 246 CLR 36.