10.1 Intervening conduct or event

The defence of intervening conduct or event is limited in its applications to physical elements of an offences for which strict or absolute liability is imposed: s6.1. Strict Liability; s6.2 Absolute Liability.

Though the prosecution is not required to prove fault with respect to the physical element of the offence in question, criminal responsibility is not incurred if that element resulted from either the conduct of another person or an event over which the defendant could not be expected to exert control. The Code follows the canonical common law formulation of the defence by Bray CJ in Mayer v Marchant:²⁵³

It is a defence to any criminal charge to show that the forbidden conduct occurred as the result of an act of a stranger, or as the result of non-human activity, over which the defendant had no control and against which he or she could not reasonably have been expected to guard.

The defence is available when any physical element of the offence – an act, omission, state of affairs, circumstance or result – is brought about by or as   a consequence of some extraneous and uncontrollable event or conduct of another. It is evident that the requirement of an intervening event or conduct was not meant to restrict the defence to events or conduct which “come between” the defendant’s conduct and other physical elements of the offence.²⁵⁴ Since s10.1 refers to the potentially exculpatory effect of intervening conduct, it is apparent that the defence can be based on the failure or omission of some expected action by another person. For example, a failure on the part of a manufacturer to sterilise food preparation utensils could provide the basis for a defence of intervening conduct for a retailer charged with selling contaminated food.

The defence can supplement a denial that an offence of strict or absolute liability was committed voluntarily: see s4.2 Voluntariness. In offences which impose strict liability,  it will also supplement the operation of the defence   of reasonable mistake of fact: s9.2 Reasonable mistake of fact (strict liability). That defence is available to a defendant only if there was, in fact, a mistake. Mere ignorance, no matter how reasonable, cannot provide grounds for a defence of mistake. This rigidity in the defence of reasonable mistake is palliated by the availability of the defence of intervening conduct.²⁵⁵ The defence will excuse defendants who simply failed to anticipate those unpredictable and unavoidable events which bring their conduct within the scope of criminal prohibition.