Section 269C of the Criminal Law Consolidation Act 1935 (SA) outlines a general defence of Mental Impairment where because of a mental illness, intellectual disability or mental impairment the defendant did not know the nature and quality of their conduct, that what they did was wrong or was unable to control their conduct. The law recognises that such persons do not have the mental element of a guilty mind that is required to be found guilty of a criminal offence.
There is a presumption of mental competence [s 269D] and to make use of the mental impairment defence mental incompetence must be shown on the balance of probabilities. The possible consequences of a finding of mental impairment are unconditional release or release on strict conditions of supervised licence or detention in secure psychiatric care [s 269O].
The mental impairment defence can only be used where the criminal act is as a result of a malfunction of the person’s mental faculties, resulting from an underlying infirmity of the mind [for examples see R v Radford (1985) 42 SASR 266; R v Falconer(1990) 171 CLR 30;  HCA 49].
A person who is intoxicated at the time of the criminal act is not considered to be mentally impaired because his or her behaviour does not result from a pathological cause, i.e. underlying mental disease, impairment or disorder [see definition of mental impairment under s 269A(1) and R v Falconer(1990) 171 CLR 30;  HCA 49].
Under section 269O of the Criminal Law Consolidation Act 1935 (SA) it is a condition of every licence for release that the defendant be prohibited from possessing firearms and ammunition. The Court may also direct a defendant to surrender a firearm [s 269OA].
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