M’Naghten’s Case

Brief Fact Summary. Defendant, M’Naghten was charged with the murder of Edward Drummond, secretary to the Prime Minister and used the insanity defense at trial. At the time of his arrest, he told police that he came to London to murder the Prime Minister because he was told to do so. The jury reached a verdict of not guilty and a meeting at the House of Lords ensued in order to determine what the standards for the insanity defense would be.

Synopsis of Rule of Law. In order to establish an insanity defense, it must be clearly proven that at the time of the act, the accused was under such a defect of reason from disease of the mind that he did not know the nature and quality of the act he was committing; or if he did know, he did not know what he was doing was wrong.

Facts. Defendant was charged with the murder of Edward Drummond, secretary to the Prime Minister, Sir Robert Peel. Defendant mistook Drummond for Peel and shot Drummond by mistake. At the time of his arrest, he told police that he came to London to murder the Prime Minister because “the tories in my city follow and persecute me wherever I go, and have destroyed my peace of mind. They do everything in their power to harass and persecute me; in fact they wish to murder me.” Defense counsel introduced expert and lay witnesses who testified about Defendant’s obsession with delusions and that he suffered from acute insanity. The judge gave the jury an instruction regarding his lack of understanding upon commission of the act in question. The jury reached a verdict of not guilty by reason of insanity. Following the trial, there was a meeting at the House of Lords attended by fifteen judges in order to determine the standards for the insanity defense.

Issue. What is the proper instruction for the jury in a case where the insanity defense is used?

Held. Lord Chief Justice Tindal delivered the opinion for the House of Lords. Jurors should be instructed that every man is presumed sane and to possess a sufficient degree of reason to be responsible for his crimes. Therefore, in order to establish an insanity defense, it must be clearly proven that at the time of the act, the accused was under such a defect of reason from disease of the mind that he did not know the nature and quality of the act he was committing; or if he did know, he did not know what he was doing was wrong.

Discussion. The M’Naghten Rule has generally been presented to the jury as a standard in determining whether the accused at the time of doing the act knew the difference between right and wrong. This standard should be used in conjunction with observations made of the defendant under the relevant circumstances on a case-by-case basis.