It is not generally a defence to criminal conduct that a defendant was intoxicated by alcohol or drugs at the time the offence was committed. However, Part 8 of the Criminal Law Consolidation Act 1935 (SA) [ss 267A - 269] allows an intoxication defence in limited circumstances.

The defence of intoxication recognises that alcohol and drugs can impair a defendant's ability to form the required mental intention to commit a criminal offence. A defendant may successfully raise a defence of intoxication if they can show that their intoxication impaired their consciousness to the point of criminal irresponsibility [s 268(1)].

Intoxication will not be available as a defence if the defendant formed an intention to commit the offence before becoming intoxicated, and became intoxicated to strengthen their resolve to commit the offence (colloquially known as "Dutch courage") [s 268(1)].

Intoxication is generally not a defence when the intoxication is self-induced [s 268(2)]. Recreational use of a drug is considered self-induced. Where intoxication arose from both recreational and therapeutic use of one or more drugs, the resulting intoxication is also considered self-induced.

A person found mentally incompetent to have committed an offence, in circumstances where the trial judge is satisfied that the mental incompetence was substantially caused by self-induced intoxication, will usually be dealt with under Part 8 rather than Part 8A [s 269C(2)] unless the judge orders otherwise in the interests of justice [s 269C(3)]. See Mental impairment.

Self-induced intoxication operates as a partial defence to certain offences that require a specific intent and foresight of the consequences of certain actions. A person who assaults another while impaired by self-induced intoxication may, if the person dies, be found guilty of manslaughter but may not be found guilty of murder [see s 268(3), (4)].

Intoxication is a complicated defence and should not be raised or relied upon without legal advice and representation.