If it can be demonstrated that a defendant committed a crime as the result of an involuntary act they may be able to plead the defence of automatism.
Automatism is defined as “the performance of actions without conscious thought or intentions”.
An automatism may occur secondary to physical or mental disorder; however, voluntary intoxication is not accepted as a cause. It is may be pleaded as a full defence to any offence provided there is a total lack of control.
Automatisms may be classified as insane or non-insane.
For a defence of insane automatism, the involuntary action must have been caused by an “internal factor”. In R v Hennessy (1989), the defendant (who had diabetes) committed the offence while in a hyperglycaemic state. The hyperglycaemia was considered an “internal factor” and the plea of insane automatism was accepted.
By contrast, for a defence of non-insane automatism, the involuntary action must have been caused by an “external factor”. A classic (hypothetical) example involves a van driver losing control of their vehicle when attacked by a swarm of bees (per Lord Goddard CJ, Hill vs Baxter [1958]).
If the defendant successfully pleads non-insane automatism this results in acquittal. In the event of a successful plea of insane automatism a special verdict of not guilty by reason of insanity would be delivered which may result in the disposal of a Hospital Order (with or without a restriction order) under Section 37 of the Mental Act 1983 (as amended 2007).