The Insanity Defense in England and Wales since 1843

For defendants in the nineteenth century seeking refuge from the death penalty, the insanity defense was like a haven eagerly sought but with difficulty secured. For defendants now, no longer at risk of the death penalty and able to take advantage of statutory defenses akin to insanity, the defense has become like a reef fearfully avoided but easily struck. The transformation of the defense from shelter to snare is best understood when traced through the attempts of defendants to establish a defense of irresistible impulse due to mental disorder. At first, irresistible impulse was pleaded as insanity under the McNaughtan Rules. When this was no longer possible, defendants turned to the defense of involuntary conduct, a defense elaborated largely in response to the development of motoring. The courts' response to this tactic has breathed new life into the McNaughtan Rules, but legislation is required to remove resulting anomalies.