Intoxication is not a complete defence unless the intoxication was the involuntary (e.g. drink spiking). However, in some circumstances intoxication can have a bearing on whether a person formed the intention required to be proven by the prosecution.
Evidence of intoxication will be when an accused person is charged with an offence of specific intent. Specific intent offences are those which require the Crown to prove that the accused person possessed a specific intent to bring about a specific result. The court can take into account the degree of intoxication of the accused when determining whether the prosecution has proved that the accused had formed the intent to bring about a specific result. For example, the charge of inflicting grievous bodily harm with intent requires a person to intend to grievous bodily harm.
Evidence of intoxication may not be taken into account for a crime of specific intent, if the accused resolved before becoming intoxicated to do the relevant conduct, or became intoxicated in order to strengthen his or her resolve to do the relevant conduct.
Intoxication is a complete defence where the intoxication was not voluntary. A person is not criminally responsible for an offence if the relevant conduct resulted from intoxication that was not self-induced. For example, if the intoxication was involuntary (e.g. drink spiking), or results from fraud, sudden or extraordinary emergency, accident, reasonable mistake, duress or force, or results from the administration of a drug for which a prescription is required in accordance with the prescription of a medical practitioner or dentist, or of a drug for which no prescription is required, administered for the purpose, and in accordance with the dosage level recommended, in the manufacturer’s instructions.