Automatism
A common law defence available where a defendant's consciousness was so impaired that they lost the ability to consciously control their actions, rendering the act involuntary. English law distinguishes 'insane automatism', arising from an internal cause or disease of the mind, from 'sane' or 'non-insane automatism', arising from an external factor, which operates as a complete defence resulting in acquittal.
Independent editorial summary — not the official statute text. Read the official version on legislation.gov.uk.
CPS legal guidance describes automatism as a common law defence: “Automatism is a common law defence.” It applies only in narrow circumstances, because “It is available where the person's consciousness was so impaired that they were acting in a state of physical involuntariness” and had lost the ability to consciously control their actions, such that they cannot be held culpable for what followed.
The law draws a sharp line between two forms of the defence, turning on where the impairment came from. “Insane automatism: this results from an internal cause or disease of the mind”, and in the Crown Court a successful plea produces the special verdict of not guilty by reason of insanity rather than an outright acquittal. By contrast, “Sane or non-insane automatism: this results from causes other than a disease of the mind, namely external factors which led to a loss of control”, and “This amounts to a complete defence and therefore it results in acquittal.”
Example
CPS guidance lists examples of sane/non-insane automatism recognised by the courts, including ‘a blow to the head causing concussion: Hill v Baxter [1958] 1 QB 277, an injection of insulin: R v Quick [1973] QB 910’.
Related terms
Official sources
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