McGhee was an employee the National Coal Board, and generally worked emptying pipe kilns. However, one day he cleaned out brick kilns. This work caused him to get very sweaty, and powdered brick caked on to his skin. He then biked home without washing, because there were no cleaning facilities provided by the employer, and developed dermatitis. The exact way that this disease develops was not known at the time, but it was proven that the washing immediately after coming out of the kiln would have at least lessened the risk of it developing. The Coal Board was successful at the lower courts, which McGhee appealed.
- When a defendant has been proved to have negligently contributed to the development of an injury, should they be liable if it can be shown that the plaintiff’s actions also led to the development, and the exact cause is unknown?
Simon of Glaisdale sums up the reasons thusly:
Where an injury is caused by two or more factors operating cumulatively, one or more of which is a breach of duty and one or more of which is not so, in such a way that it is impossible to ascertain the proportion in which the factors were effective in producing the injury or which factor was decisive, the law does not require the plaintiff to prove the impossible, but holds that he is entitled to damages for the injury if he proves on a balance of probabilities that the breach of duty contributed substantially to causing the injury
Material increase in risk was treated as equivalent to a material contribution to damage