R v Byrne [1960] 2 QB 396

Court: Court of Appeal (Criminal Division)

Facts: D, a sexual psychopath, killed and mutilated a young girl. Expert evidence established that D had an abnormality of mind that substantially impaired his ability to control his impulses.

Issue : Does the concept of "diminished responsibility" under the Homicide Act 1957 apply to a defendant who, due to a sexual psychopathology, claims to have been unable to control his actions at the time of the crime?

Held: D's murder conviction was reduced to manslaughter due to diminished responsibility. The court held that the term "abnormality of mind" under the Homicide Act 1957 is broad enough to include not only impairments in reasoning and understanding but also the inability to control physical actions due to an overwhelming impulse.

Key Judicial Statement: Lord Parker CJ defined "abnormality of mind" as a state of mind so different from that of ordinary human beings that the reasonable man would term it abnormal.