R v Burgess [1991] 2 WLR 1206
Acquittal by virtue of insanity where accused committed crime whilst sleep-walking
Facts
The appellant (B) was charged with wounding with intent to do grievous bodily harm. His defence was that during the event he was sleep walking and suffering from non-insane automatism. However, the judge ruled that on the medical evidence available the only defence available was insanity. The jury found B not-guilty by reason of insanity.
Issues
On appeal, B argued that automatism should not be considered insanity. The Crown argued that B suffered from an abnormal state of mind and it was irrelevant how it arose. The Court accepted that there was a failure in B’s mind which caused him to act as he did. The key issue was therefore whether that failure was a disease of the mind or, rather, a defect or failure of the mind not due to disease.
Decision/Outcome
B’s appeal was dismissed. The Court found that the failure in B’s mind was due to an abnormality which manifested itself in violence and might recur. This amounted to a disease of the mind and the trial judge’s application of insanity as a defence was therefore correct. In particular, the Court noted the absence of obvious external factors (such as, for instance, concussion) which could have caused the failure in B’s mind. The Court adopted the reasoning of the Supreme Court of Canada in Rabey v the Queen [1980] 2 S.C.R. 513 and found that any malfunctioning of the mind which has its source in some condition or weakness internal to the accused may be a ‘disease of the mind’ and, accordingly, a finding of insanity may follow.
Updated 20 March 2026
This case summary remains accurate as a statement of the law as it stood in 1991. However, readers should note a significant subsequent development: the defence of insanity (including in sleepwalking cases) has been subject to ongoing law reform debate. The Law Commission published a report, Criminal Liability: Insanity and Automatism (2013), recommending replacement of the M’Naghten Rules with a modernised statutory framework, but as of 2025 no amending legislation has been enacted and the common law rules applied in Burgess remain the operative law in England and Wales.
Additionally, readers should be aware that the verdict of ‘not guilty by reason of insanity’ is now returned under the amended procedure introduced by the Criminal Procedure (Insanity) Act 1964, as amended by the Criminal Procedure (Insanity and Unfitness to Plead) Act 1991 (which was in force at the time of this case) and further by the Domestic Violence, Crime and Victims Act 2004. These amendments broadened the range of disposals available following such a verdict, meaning a defendant is no longer automatically committed to a psychiatric hospital. The core legal principles stated in Burgess regarding the internal/external distinction and the definition of ‘disease of the mind’ for the purposes of the insanity defence remain good law.
