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M'Naghten's case
Factual and Procedural Background
The Defendant was indicted before the Central Criminal Court for the murder of the Victim, whom he shot with a pistol on 20 January 1843. At trial, the Defendant pleaded Not guilty and adduced medical testimony asserting that he suffered from morbid delusions that deprived him of self-control and moral perception. Judge Tindal, charging the jury, instructed that criminal responsibility turned on whether the Defendant knew the act was wrong. The jury returned a verdict of Not guilty by reason of insanity.
Public controversy followed. The House of Lords, exercising its right to seek judicial assistance, summoned all common-law Judges on 26 May and again on 19 June 1843. Five abstract questions on the criminal responsibility of the mentally disordered were put to the Judges, who delivered their coordinated answers—now known as the “M’Naghten Rules.”
Legal Issues Presented
- Whether a defendant who knowingly violates the law but acts under an “insane delusion” aimed at redressing a supposed grievance remains criminally liable.
- What questions should be submitted to a jury when insanity is raised as a defence.
- How a jury should be directed regarding the defendant’s mental state at the time of the act.
- Whether an offence committed under a factual delusion excuses the offender.
- The admissibility of expert psychiatric opinion from a medical witness who first observes the defendant only during trial.
Arguments of the Parties
Defendant’s Arguments
- Medical experts testified that the Defendant suffered from a progressive mental disease producing irresistible delusions that eliminated his capacity to distinguish right from wrong and to control related acts.
- Some experts, who had never examined the Defendant before trial, offered opinions based solely on in-court testimony, asserting that the Defendant could not appreciate the wrongfulness of his conduct.
The opinion does not detail the prosecution’s arguments.
Table of Precedents Cited
| Precedent | Rule or Principle Cited For | Application by the Court |
|---|---|---|
| London and Westminster Bank Case, 2 Cl. & F. 191 | House of Lords may request Judges’ opinions on abstract questions of law. | Cited as authority for summoning Judges to answer the present questions. |
| Reg. v. Townley (1863) | Subsequent application of the M’Naghten Rules. | Mentioned to show later acceptance of today’s statements. |
| Reg. v. Southey (1865) | Further judicial reliance on the M’Naghten Rules. | Cited as supportive precedent. |
| Reg. v. Leigh (1866) | Continued authority of M’Naghten Rules. | Referenced as an example of later application. |
| Parsons v. State (1887, 81 Ala. 577) | American rejection of the strict M’Naghten standard. | Noted to illustrate critical reception abroad. |
Court's Reasoning and Analysis
The majority of the Judges, delivered through Judge Tindal, articulated the following principles:
- Presumption of sanity: Every individual is presumed sane and responsible until insanity is proven.
- Test for insanity: To succeed, the defence must show that at the time of the act the accused suffered a “defect of reason, from disease of mind,” such that he either (a) did not understand the nature and quality of the act, or (b) did not know it was wrong.
- Partial delusion: A defendant labouring under a specific delusion is judged as if the delusive facts were real; responsibility remains if the supposed facts would not justify the killing.
- Knowledge of law vs. morality: Liability exists if the defendant understood that the act was contrary to the law of the land; juries should be directed with reference to the wrongfulness of the particular act, not abstract legal knowledge.
- Expert evidence: A medical expert who first sees the defendant during trial may give opinion evidence, but only on scientific matters; questions that assume the truth of contested facts must be left to the jury.
Judge Maule concurred generally but expressed reservations about answering broad abstractions without factual context, warning that rigid formulations might hamper future trials.
Holding and Implications
HOLDING: The Judges unanimously set out the criteria—now termed the M’Naghten Rules—governing the insanity defence in English criminal law.
IMPLICATIONS: The decision established the authoritative legal test for criminal insanity, guiding jury directions and the admissibility of expert psychiatric evidence in England and influencing common-law jurisdictions. While later cases interpret the Rules flexibly and some foreign jurisdictions have rejected them, the framework remains the cornerstone of the insanity defence in the United Kingdom.
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