Abstract
Traditionally tort (personal injury) cases have been regarded as isolated disputes concerned with individual harm, where the law's role was simply to allocate losses between tortfeasor and victim according to principles of corrective justice. With the advent of the toxic tort – a cause of action which arises when a plaintiff has developed a disease following exposure to a toxic agent (chemical or in the form of energy) has come a fundamental challenge to the traditional basis of causation where under negligence or strict liability the toxic tort plaintiff (like all tort plaintiffs) must establish a causal connection between the tortious conduct and the loss for which recovery is sought. When applying the ‘balance of probability’ test to a toxic tort, two potential problems arise. First the test does not work where there are multiple or even alternative possible causes of a plaintiff's injury. Here the burden of proof demands a degree of certainty in excess of fifty per cent in an area where estimates, probabilities and scientific uncertainty are the norm. Second, difficulties occur in trying to establish the origins of the plaintiff's disease, in particular, the biological mechanism responsible for initiating or mobilising the illness. Underlying the basis of all toxic torts, distinct areas of scientific knowledge, grounded in an epistemological and procedural framework provide the evidence upon which the expert offers his opinion. This article examines the problems that such evidence poses for the legal system and reflects on some of the jurisprudential issues that arose in Reay and Hope v British Nuclear Fuels.