chapter  1
Pages 10

Proving the causal connection between the defendant’s negligence and the plaintiff’s damage is often a straightforward matter. For example, a typical motor vehicle accident may be attributable to the negligent driving of one or both of the drivers. Proof of causation through the application of the traditional so-called ‘but for’ test yields a simple result that the accident would not have occurred but for the negligent driving which becomes a necessary condition of the plaintiff’s loss. Proof of the causal connection may become more complicated, however, when subsequent events conspire with the situation generated by the defendant’s negligence to produce the plaintiff’s loss. What if the plaintiff’s injuries are made worse by subsequent negligent medical treatment administered at a nearby hospital to which the plaintiff was taken? What if the pain and disability accompanying such injuries result in a state of depression which eventually drives the plaintiff to suicide? In other contexts, how is causation resolved when a merchant vessel which has been damaged through the negligent navigation of another vessel sinks while en route to port for repairs during an extraordinary and unseasonal storm? Or what is the situation where a person is injured while attempting to rescue another person who has been imperilled by the negligence of the tortfeasor? Application of the ‘but for’ test would yield the result that the defendant would be liable for everything which followed the negligent conduct – the negligent medical treatment, the suicide, the sinking of the vessel and the injury to the rescuer – because none of the events would have transpired without that negligence. But is that fair? In such cases, the defendant could plausibly argue that he or she should not be liable where an act or event has intervened between the defendant’s negligence and the plaintiff’s injury. The defendant may argue that his or her conduct no longer operates as the effective legal cause of the plaintiff’s injury, having been replaced by the intervening act or event which is said to have broken the chain of causation. Such a chain-breaking event is referred to by English judges as a novus actus interveniens and by US commentators as a ‘superseding cause’. If the intervening event breaks the chain of causation, such event rather than the defendant’s negligence will be considered the effective cause of the plaintiff’s injury in attributing legal causal responsibility. It has been a long-standing judicial technique to focus on certain intervening events which, in conjunction with the defendant’s default, precipitate or aggravate the plaintiff’s injury.1 The crucial question becomes whether the defendant is to be held liable for loss caused by or contributed to by the

intervening event. As we shall see, the answer to this question depends on a variety of considerations and is subject to the application of varying legal tests.2