chapter  5
Voluntary and Deliberate Human Action
Pages 22

Historically it has generally been easier to successfully plead novus actus interveniens when the intervention of the third party is deliberate in the sense that the third party’s act was intended to produce the consequences the intervention did in fact produce. It has been said that deliberate interventions are more likely to sever the causal chain than negligent interventions1 and that ‘the more flagrant and overwhelming the intervention the more likely it is to amount to a novus actus.’2 For long the principle held sway that if, subsequent to the defendant’s negligence, there intervened prior to the plaintiff’s injury the culpable act of a third person, the ‘last human wrongdoer’ was alone liable.3 This principle acknowledged ‘the fact that the wilful wrongdoing of others cannot ordinarily be accounted a normal risk of the dangerous situation created by the defendant.’4 In Dominion Natural Gas Ltd v Collins and Perkins5 Lord Dunedin was not prepared to hold a defendant liable ‘if the proximate cause of the accident is not the negligence of the defendant but the conscious act of another volition’.6 And in Weld-Blundell v Stephens7 Lord Sumner stated:

In general even though A is in fault, he is not responsible for injury to C which B, a stranger to him, deliberately chooses to do. Though A may have given the occasion for B’s mischievous activity, B then becomes a new and independent cause…he insulates A from C.8