R v Sullivan [1984] AC 156

Epilepsy and the defences of insanity and automatism after M’Naghten


The defendant, a psychomotor epilepsy sufferer, had an epileptic seizure during which he kicked the victim in the head violently. He was charged with causing Grievous Bodily Harm contrary to sections 18 and 20 of the Offences Against the Person Act 1861. He pleaded not guilty to those charged but upon taking advice from counsel, pled guilty to Assault occasioning Actual Bodily Harm contrary to s.47 Offence Against The Person Act 1861 and was convicted of the offence. At trial evidence was adduced, which was accepted, that the defendant did not recall the incident; further, two medical experts gave evidence that the defendant’s attack on the victim most likely occurred during the postictal stage of the epileptic seizure, at which stage a sufferer makes automatic movements without being conscious of them. The trial judge ruled that the appropriate defence in this case is insanity and not automatism.


The issue for the appeal court was whether epilepsy amounted to a “disease of the mind” within the meaning of R v M’Naghten (1843) 8 ER 718 and therefore whether insanity is the correct defence for epilepsy sufferers.


The court agreed with the trial judge’s assessment that epilepsy is a disease of the mind and that therefore the correct defence is one of insanity. Epilepsy is not caused by an external influence, but is rather an internal illness, which affects the mind, hence bringing it under the M’Naghtendefinition.