Imagine a patient suffers from Tourette’s, which causes them to involuntarily swear and shout epithets (for example, sexist or racist slurs such as the n-word). In the U.K., this is very likely to be seen as a public order offence, in case the exclamation was of a racial or antijewish slur, then a racially and/or religiously aggravated one.

Typically, questions as to a defendant’s mental illnesses, particular insofar as they relate to an offence, are to be considered as mitigating factors when it comes time for sentencing.

But can such relevant mental illnesses ever be taken to preclude guilt in the first place (verdict stage)?

1 Answer 1


Involuntariness negates the actus reus of the offence. Involuntary conduct is not criminal, and the law recognizes that voluntariness for the conviction of a crime is a principle of fundamental justice. See R. v. Brown, 2022 SCC 18.

Another circumstance where mental illness would prevent a finding of guilt is where the accused is "not guilty by reason of mental disorder."

These two "defences" are already described in a other Q&A: Is psychological impairment a defense for murder? That question posed the charge of murder, but the answer is applicable to all offences.

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