A person who kills or is a party to the killing of another is not to be convicted of murder if he was suffering from an abnormality of mental functioning which:
(a) arose from a recognised medical condition
(b) substantially impaired D's ability to:
- understand the nature of conduct
- form a rational judgement
- exercise self control and
(c) provides an explanation for D's act. The burden of proof is on the defendant but the D only has to prove it on the balance of probabilities.
Abnormality of mental functioning: a state of mind so different from an ordinary human beings that the reasonable man would call it abnormal. E.g. in Byrne.
Cause of the AMF: Must arise from a recognised medical condition, for example: psychological and physical conditions, mental disorders, depressive illness, paranoia, Battered Women's Syndrome, epilepsy, sleeping disorders and diabetes. There must be medical evidence given at the trial of an AMF arising from a RMC. Cases Include:
- R v Speake…