Section 22 of the Bharatiya Nyaya Sanhita, 2023 (BNS) contains the insanity defence - the general exception for an act of a person of unsound mind. It is the direct successor of the well-known Section 84 IPC, carried into the new code without change when the BNS came into force on 1 July 2024.
What Section 22 BNS provides
Nothing is an offence which is done by a person who, at the time of doing it, by reason of unsoundness of mind, is incapable of knowing:
- the nature of the act; or
- that what he is doing is either wrong or contrary to law.
It sits in the BNS chapter of general exceptions, which means it is not an offence but a defence: where it applies, the act is not an offence at all.
Legal insanity, not medical insanity
The section adopts the test derived from the historic M'Naghten rules, and courts apply it strictly. Three points matter in practice:
- The crucial time is the moment of the act. A history of mental illness before or after is relevant evidence, but the incapacity must exist when the act was done.
- Legal insanity is narrower than medical insanity. A diagnosis - depression, schizophrenia, epilepsy - does not by itself attract the section. What must be shown is that the unsoundness of mind made the person incapable of knowing the nature of the act, or that it was wrong or contrary to law.
- Conduct is the evidence. Courts look at the person's behaviour before, during and after the act - planning, concealment or flight tends to show awareness that the act was wrong; utterly irrational conduct supports the plea.
Who has to prove what
The prosecution must always prove the offence beyond reasonable doubt. An accused who pleads this exception carries the burden of establishing it, but only on a preponderance of probabilities - the civil standard, not the criminal one. Following Dahyabhai Chhaganbhai Thakkar v. State of Gujarat (1964), even where the accused cannot fully establish the exception, evidence of mental condition that raises a reasonable doubt about the required guilty mind entitles the accused to an acquittal on general principles.
What happens when the plea succeeds
A successful plea results in an acquittal on the ground of unsoundness of mind - not a conviction with a lighter sentence. The court then deals with the person under the special procedure the BNSS provides for such acquittals, which can include safe custody and treatment rather than simple release. This is one reason the plea needs careful, informed handling.
What changed from Section 84 IPC
Nothing. The provision was renumbered from Section 84 IPC to Section 22 BNS with no change in wording, and the entire body of case law on Section 84 continues to apply.
Is mental illness part of your case - yours or a family member's? The insanity defence is technical, evidence-heavy and often misunderstood. Talk to a criminal lawyer in your city or browse advocates in the Free Law directory.