Bonnington Castings Ltd v Wardlaw  AC 613 House of Lords
The claimant contracted pneumoconiosis by inhaling air which contained minute
particles of silica during the course of his employment. The defendant was in breach of a statutory duty in failing to provide an extractor fan. Had they installed an extractor fan the number of particles of silica that the claimant was exposed to would have been reduced, however, there would still be some particles present. There were thus two possible causes: the guilty dust, which should not have been in the working environment and the innocent dust, which would have been present in any event. The trial judge held that where the duty arose by statute then it was for the defendant to show that his breach of duty (the guilty dust) did not cause the disease. As the defendant was unable to do this they were liable. The defendant appealed contending the burden of proof rests on the claimant.
The burden of proof remains on the claimant. However, the claimant only had to demonstrate that the guilty dust had made a material contribution to the disease. He did not have to demonstrate on the balance of probabilities that the guilty dust was the sole cause of the disease. Back to lecture outline on causation in tortious liability Negligence