What is the ratio in M'Naghten's Case?

The ratio establishes that insanity defence requires proof the defendant either didn't know the nature and quality of his act, or didn't know it was wrong, due to defect of reason from disease of mind.

What did the court decide in M'Naghten's Case?

The House of Lords established the M'Naghten Rules defining the legal test for criminal insanity, requiring specific cognitive incapacity at the time of the offence.

Why is M'Naghten's Case important for criminal law?

It created the foundational test for insanity defence still used today, balancing criminal responsibility with recognition of severe mental illness as a defence to criminal liability.

What is the ratio in M'Naghten's Case?

The ratio establishes that insanity defence requires proof the defendant either didn't know the nature and quality of his act, or didn't know it was wrong, due to defect of reason from disease of mind.

What did the court decide in M'Naghten's Case?

The House of Lords established the M'Naghten Rules defining the legal test for criminal insanity, requiring specific cognitive incapacity at the time of the offence.

Why is M'Naghten's Case important for criminal law?

It created the foundational test for insanity defence still used today, balancing criminal responsibility with recognition of severe mental illness as a defence to criminal liability.

Criminal1 min read

Insanity — M'Naghten's Case

(1843) 10 Cl & Fin 200House of Lords1843

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“Established the M'Naghten Rules defining criminal insanity defence requirements.”

Facts

Daniel M'Naghten shot Edward Drummond, private secretary to Prime Minister Robert Peel, believing he was being persecuted by the Tory government. M'Naghten suffered from paranoid delusions and intended to kill Peel but mistook Drummond for him. He was acquitted by reason of insanity, causing public outcry.

Issues

What test should be applied to determine when mental illness provides a defence to criminal charges?

Held

The House of Lords established the M'Naghten Rules, requiring proof that the defendant either did not know the nature and quality of his act, or did not know it was wrong.

Significance

The M'Naghten Rules remain the primary test for insanity in English criminal law today. This case is fundamental to understanding mental health defences and the balance between criminal responsibility and mental illness in the justice system.

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OSCOLA Citation

M'Naghten's Case (1843) 10 Cl & Fin 200

Criminal LawMental Health LawDefences

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