D was labouring under a defect of reason due to a disease of the mind so that they did not understand the nature and quality of their actions, or that they did not know it was wrong.
Defect of reason?
complete loss of powers of reasoning (Clarke)
Disease of the mind?
anything that produces malfunctioning of the mind, e.g. epilepsy (Sullivan), sleepwalking (Burgess) and hyperglycaemia (Hennessy)
Windle?
D does not know nature and quality OR that what they were doing was legally wrong
Criminal Procedure (Insanity and Unfitness to Plead) Act 1991?
a successful defence will lead to a special verdict of not guilty by reason of insanity.
