Substantial impairment by abnormality of mind

SUBSTANTIAL IMPAIRMENT BY ABNORMALITY OF MIND

The legal defence of substantial impairment by abnormality of mind is a partial defence to the criminal offence of murder and is enshrined in Section 23A of the Crimes Act 1900 (NSW), which states that:

A person who would otherwise be guilty of murder is not to be convicted of murder if—

• At the time of the acts or omissions causing the death concerned, the person’s capacity to understand events, or to judge whether the person’s actions were right or wrong, or to control himself or herself, was substantially impaired by a mental health impairment or a cognitive impairment, and
• The impairment was so substantial as to warrant liability for murder being reduced to manslaughter.

Self-induced intoxication does not give rise to the defence of substantial impairment by abnormality of mind.