The two main general defences to actions in tort are contributory negligence and volenti non fit injuria.
Contributory negligence is basically carelessness on the part of the plaintiff which combines with the defendant’s negligence or breach of duty in bringing about the plaintiff’s damage. In many cases, the plaintiff’s negligence will have been a contributing cause of the accident which led to the damage, for example, where he steps into the road without keeping a proper lookout and is struck by a car being negligently driven by the defendant; or where the plaintiff’s and the defendant’s vehicles collide head-on as a result of both drivers’ careless overtaking of other vehicles. But the essence of contributory negligence in law is not that the plaintiff’s carelessness was a cause of the accident; rather, it is that it contributed to his damage. Thus, for example, where a plaintiff car driver carelessly rests his arm on the outside of his vehicle as he is driving, and another motorist negligently collides with the car and injures the plaintiff’s arm,1 or where a plaintiff motorcyclist is knocked down by a negligent motorist and suffers head injuries, owing to the fact that he is not wearing a crash helmet,2 the carelessness of each plaintiff is not a cause of the accident but it does contribute to his damage. In Denning LJ’s words:3
A person is guilty of contributory negligence if he ought reasonably to have foreseen that, if he did not act as a reasonable, prudent man, he might be hurt himself; and in his reckonings he must take into account the possibility of others being careless.