There is a variety of ways in which intoxication can have a bearing on the attribution of criminal responsibility. The issue is most likely to arise in charges involving injury to the person or damage to property. In general, evidence of intoxication tends to reinforce the case for the prosecution. If the defendant was under the influence of alcohol, the most likely inference is that injury was inflicted intentionally or damage done intentionally as a consequence of drunken aggression.154 When offences of negligence or strict liability are charged, evidence of intoxication by any substance that impairs cognition or co-ordination will similarly tend to reinforce the prosecution case. But intoxication also impairs the capacities to perceive and interpret reality and to coordinate actions to intended objectives. These incapacities can have an obvious bearing on criminal responsibility when the prosecution must prove that the defendant was aware of a risk or intended a consequence. Contrary to appearances, a drunk who takes the wrong umbrella when leaving a restaurant may not have given way to a sudden impulse to steal a better umbrella; the taking may have been a simple mistake, the drunk having lost the capacity for fine distinctions of colour or quality. In cases of extreme intoxication, Australian courts have taken the view that the person can be deprived of the capacity to act voluntarily.
Intoxication is usually a voluntary indulgence undertaken for pleasure, recreation or relief from pain or care. Since the condition is voluntary, few jurisdictions are prepared to allow incapacity resulting from intoxication to excuse without qualification. There is no uniformity – there is indeed a rich and confusing variety – among the ways in which states and territories limit pleas of incapacity voluntarily incurred as a consequence of intoxication.155 The Code imposes relatively few limits on the purposes for which prosecution and defence may rely on evidence of intoxication. In Federal jurisdiction, where most offences will not involve personal violence or the cruder varieties of crime against property, the issue will not arise often.
The most significant of the privative provisions in the Code is the rule, discussed earlier, that evidence of self induced intoxication cannot be considered when a defendant claims that conduct was involuntary: 4.2 Voluntariness. That prohibition applies no matter what the offence charged. The privative rules in Division 8 - Intoxication are far more limited in their applications. The general principle is that evidence of intoxication, whether or not self induced, will be considered whenever it is relevant to the determination of intention, knowledge, recklessness, negligence or other fault elements. The exceptions to the general principle take the same form as the voluntariness rule. The Code declares that evidence of self induced intoxication “cannot be considered,” in certain circumstances, when intention156 or belief157 is in issue. It is important to notice that this exclusionary rule, which is limited in its possible applications, restricts prosecution and defence alike.
If the state of intoxication was not self-induced, as for example when the defendant was tricked into consuming an intoxicating substance, the rules which prevent consideration of evidence of intoxication cease to apply. Chapter 2 goes even further, however, when intoxication is not self-induced, allowing a defence of “involuntary intoxication”. A person whose state of intoxication was not self-induced must be acquitted if the offence with which they are charged is a result of that state of intoxication.
