Mental Impairment

This defence is used when the Accused, at the time of committing the offence/s, was suffering from an mental impairment such that:

  • They did not understand what they were doing; and
  • They did not know what they were doing was wrong.

 Under s. 20 of the Crimes (Mental Impairment and Unfitness to be Tried) Act 1997:

A person is presumed to be not suffering from a mental impairment unless it is proved by the defence.

The standard upon which the defence must prove mental impairment is ‘on the balance of probabilities’.