Like intoxication, the defences of mental disorder and automatism apply to accused who commit criminal acts, but who cannot be found criminally responsible because their mental processes were impaired. It has long been accepted that an offender who, because of a mental disorder, is incapable of appreciating the nature and quality of a criminal act, or of knowing that it is wrong, should not be convicted. The verdict is not a pure acquittal, but rather a verdict of not criminally responsible on account of mental disorder or what used to be called not guilty by reason of insanity. The accused does not automatically go free and can be subject to detention or release with conditions until he or she is determined no longer to be a significant danger to society. In Canada, the mental disorder defence is set out in section 16 of the Criminal Code, and has been revised by both the Supreme Court and Parliament to take into account various Charter concerns.
The defence of automatism is more novel, and applies to an accused who has committed a criminal act while in a state of impaired consciousness that results in involuntary behaviour. If that state is caused by a mental disorder, the accused will be held not criminally responsible by reason of mental disorder. If the cause of the automatism is some other factor such as a blow to the head, the present disposition is to acquit the accused. The defence of non-mental disorder automatism is a common law defence that is not codified. If the cause of automatism producing involuntary behaviour is self-induced intoxication by
alcohol or drugs, then the provisions of the intoxication defence discussed in chapter 7 will apply.
Section 16(3) of the Criminal Code...