The rules come from the famous case of M'Naughten, whereby the defendant attempted to kill the Conservative Prime Minister, Sir Robert Peel, but instead shot and killed Edward Drummond, the Prime Minister's Secretary. M'Naghten was suffering from insane delusions at the time of the killing. The House of Lords formulated the M'Naghten rules, which apply in determining whether a person should escape criminal liability on the grounds of being insane.
To be successful in the defence, the defendant needs to prove on the balance of probabilities that:
- He had a defect of reason - e.g. Clarke, Sullivan.
- Caused by a disease of the mind - e.g. Kemp, Sullivan, Hennessy, Quick.
- And that he did not know the nature and quality of his act, or he did not know that what he was doing was wrong - e.g. Windle.
All must be satisfied.
Clarke – Defendant went shopping and put items in her bag without paying for them. On appeal, the court ruled that being absent minded was not being…