Under the Bharatiya Nyaya Sanhita (BNS) 2023, Section 22 (corresponding to former IPC Section 84) provides the defence of unsoundness of mind. Under this provision, for a criminal act to be excused on grounds of mental disorder, which of the following must be established?

• A The accused had a diagnosed psychiatric illness at the time of the act
• B By reason of unsoundness of mind, the accused did not know the nature of the act OR did not know that it was wrong or contrary to law ✓
• C The accused was under involuntary intoxication at the time of the act
• D The accused was detained in a psychiatric institution within 3 months of the act

Explanation

BNS Section 22 (equivalent to IPC Section 84) requires satisfaction of the M'Naghten criteria adapted to Indian law: the accused must have been of unsound mind at the time of the act AND must have either not known the nature of the act (i.e., did not appreciate what they were doing) OR not known it was wrong or contrary to law. A mere diagnosis of mental illness is insufficient — the cognitive impairment must directly negate understanding of the act. The burden of proof for this defence lies on the accused (on the balance of probabilities under the Evidence Act). Intoxication defence is governed separately by BNS Section 23.

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

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Written and medically reviewed by the StethoPrep medical team.