Technically, there is no "intoxication" defence to criminal charges in Canadian law. Rather, in some cases, evidence of an accused's intoxication is relevant either a) to rebut the mental element or, more rarely, the act element which the prosecution must prove for conviction; or b) to support the availability of some defences. The mere loss of inhibition caused by intoxication is not a defence.

A preliminary distinction must be drawn between "voluntary" and "involuntary" intoxication. If a person had an unexpected reaction to medicine or unwittingly consumed intoxicants (without, it appears, fault on the accused's part), the accused is said to have been "involuntarily" intoxicated; such an accused could tender intoxication evidence to demonstrate that he or she lacked the fault for a crime, or, where intoxication induced an "automatic" state (see below), that he or she could not have voluntarily performed the criminal act and so could not be liable. If, however, the accused intentionally or "voluntarily" consumed intoxicants, the rules governing the admission of intoxication evidence are more strict.

Objective Standards

Where an offence or a defence involves the application of an objective standard, intoxication evidence generally cannot diminish the accused's fault. The reasonable person is not intoxicated. Intoxication evidence may render the accused more culpable, if the reasonable person would have foreseen that intoxication would increase the likelihood of the proscribed result. The rules governing intoxication evidence respecting MENS REA offences are more complex.

Ordinarily, evidence of voluntary intoxication is admissible only respecting "specific intent"mens rea offences, not "general intent" offences. "General intent" offences simply require proof that an accused intended to do the act in question with knowledge of the circumstances. "Specific intent" offences also require proof of some further intention. For example, assault (which, in one form, requires only proof of the intentional touching of another without consent), is a general intent offence; murder (which requires proof of not only the intentional infliction of harm but the intention to kill) is a specific intent offence. While criticized by judges and academics, the general/specific intent distinction remains part of Canadian law. Through the distinction, the courts restrict the availability of intoxication as a defence.

Specific Intent

Foundational English common law restricted intoxication evidence to the issue of whether an accused had the capacity to form specific intent. The modern Canadian rule is that the evidence is relevant to this issue and also to whether the accused in fact had the specific intent. If intoxication evidence raises a reasonable doubt about whether the accused either had the capacity to have or in fact had the specific intent, the accused cannot be convicted of a specific intent offence - but might be convicted of an included general intent offence. Thus, an accused charged with murder might be convicted of manslaughter if the accused was intoxicated at the time of the offence. In practice, the degree of intoxication must be severe before it raises the requisite reasonable doubt.

Intoxication evidence has additional relevance in murder cases. Murder is first degree murder if, inter alia, it was planned and deliberate. Even if the accused is proved to have had the intent to murder, intoxication evidence may raise a doubt about whether the accused planned or deliberated. A conviction for second-degree murder would result. Moreover, an accused charged with murder who successfully raises evidence of provocation is convicted only of manslaughter: while intoxication is not relevant to whether a victim's act could legally constitute provocation, it may be relevant to whether the accused in fact responded to a legally recognizable provocation.

An accused may have become so intoxicated that he or she became an "automaton" or entered a state "akin" to automatism. The accused was incapable of acting voluntarily or of forming any intention, whether general or specific. SeeAUTOMATISM, DEFENCE OF.

Automatism, or Involuntary Behaviour

The common law traditionally declined to make any special concession for voluntary intoxication automatism, regardless of the severity of the intoxication - the intoxication evidence was admissible only in specific intent offences. However, in a controversial 1994 decision, the Supreme Court of Canada held that the common-law rule violated the CHARTER; automatism established by the accused on a balance of probabilities (using expert evidence) rebuts the voluntariness or mens rea for even general intent offences, such as sexual assault. The court's decision was perceived to put women and children at risk of abuse by intoxicated men.

Parliament moved quickly, adding s33.1 to the Criminal Code in September 1995. It provides that lack of basic intent or voluntariness to commit an offence produced by self-induced intoxication shall not be a defence to an offence involving assault, interference or threat of interference with the bodily integrity of another person, where the accused departed markedly from the standard of care generally recognized in Canadian society. A marked departure occurs where the accused, while in a state of self-induced intoxication that renders him unaware of or incapable of consciously controlling his behaviour, voluntarily or involuntarily interferes or threatens to interfere with the bodily integrity of another person.

Section 33.1 has not yet been reviewed by the Supreme Court under the Charter.