A defendant is charged with murder. His lawyer pleads insanity as a defence. Under the M'Naghten rules (incorporated in BNS 2023 as the test for legal insanity), an accused is considered not criminally responsible if, at the time of the act, they:

• A Suffered from any mental illness diagnosed by a psychiatrist
• B Had an irresistible impulse caused by mental disease even if they knew the act was wrong
• C Were intoxicated by voluntary consumption of alcohol or drugs
• D Did not know the nature and quality of the act, OR did not know it was wrong, due to a defect of reason from a disease of the mind ✓

Explanation

The M'Naghten rules (1843), adopted in Indian law (BNS Section 22 / former IPC Section 84), provide the test for legal insanity: the accused is not criminally responsible if, at the time of the offence, due to a 'disease of the mind,' they either (i) did not know the nature and quality of the act they were doing, or (ii) did not know that what they were doing was wrong. The irresistible impulse test is recognized in some jurisdictions but NOT in Indian law under M'Naghten. Voluntary intoxication is not a defence.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.