Automatism

Automatism, as the name suggests, deals with circumstances where the actions of the accused were not "willed"; that is to say, not a voluntary act.

Automatism, as the name suggests, deals with circumstances where the actions of the accused were not "willed"; that is to say, not a voluntary act.

Reference is frequently made to M'Naghten's case [1843] UKHL J16, where the UK House of Lords set out what came to be known as the M’Naghten Rules. These rules hold that a person wishing to rely on the defence of insanity (as the defence was then known)must show:

They laboured under a defect of reason

Caused by a disease of the mind; so that either

He did not know the nature and quality of his acts, or that he did not know what he was doing was wrong.

These rules have found particular application in cases where the accused claims he or she acted on “reflex” (such as was claimed in Ryan v R [1967] HCA 2), where the defendant claims to have “transient mental malfunction of his otherwise sound mind“ (as was claimed in R v Falconer [1990] HCA 49), or in cases of somnambulism (as was claimed in R v DB [2022] NSWCCA 87

The position was codified by the passing of the Mental Health (Forensic Provisions) Act 2020. Section 28 provides a defence of mental health impairment or cognitive impairment:

(1)  A person is not criminally responsible for an offence if, at the time of carrying out the act constituting the offence, the person had a mental health impairment or a cognitive impairment, or both, that had the effect that the person—

(a)  did not know the nature and quality of the act, or

(b)  did not know that the act was wrong (that is, the person could not reason with a moderate degree of sense and composure about whether the act, as perceived by reasonable people, was wrong).

(2)  The question of whether a defendant had a mental health impairment or a cognitive impairment, or both, that had that effect is a question of fact and is to be determined by the jury on the balance of probabilities.

(3)  Until the contrary is proved, it is presumed that a defendant did not have a mental health impairment or cognitive impairment, or both, that had that effect.

M’Naughten

M'Naghten's case [1843] UKHL J16

“And as these two questions appear to us to be more conveniently answered together, we have to submit our opinion to be, that the jurors ought to be told in all cases that every man is to be presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crimes, until the contrary be proved to their satisfaction; and that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong.”