Any mental illness automatically excuses a crime.

Courts require 'legal insanity' — proof that the person could not understand the nature or wrongness of the act at that specific time, not just a general psychiatric diagnosis.

Section 84 means the person goes free with no consequences.

Even if acquitted under Section 84, the person may still be detained under mental health laws for treatment and public safety, not simply released.

The prosecution must prove the accused was sane.

Under Section 105 of the Evidence Act, the burden is on the accused to prove unsoundness of mind, not on the prosecution to disprove it.

Indian Penal Code, 1860

Section 84

repealed

Act of a person of unsound mind

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 he is doing what is either wrong or contrary to law.§

Why this exists

Section 84 is India's version of the 'insanity defence,' rooted in the English M'Naghten Rules (1843), which arose after Daniel M'Naghten was acquitted of murder due to insanity. The law recognizes that criminal responsibility requires a guilty mind (mens rea) — a basic capacity to understand one's actions and their moral or legal wrongness. Someone who lacks this capacity because of genuine mental illness cannot be held blameworthy in the same way a sane person would be, so punishing them would serve no purpose of justice or deterrence.

How courts read it

Indian courts have consistently held that Section 84 requires proof of 'legal insanity,' not just 'medical insanity' — a person can have a psychiatric diagnosis yet still be legally sane if they understood the nature and wrongness of their act. Courts have emphasized that the burden of proving unsoundness of mind lies on the accused (under Section 105 of the Evidence Act), and mere abnormality, eccentricity, or history of mental illness is not enough. Behavior before, during, and after the act — such as attempts to hide evidence or flee — is often used to infer whether the person understood the act's wrongfulness. Landmark cases like Surendra Mishra v. State of Jharkhand (2011) reinforced that the crucial test is the accused's cognitive capacity at the exact time of the offense, not their general mental history.

Common misconceptions

Myth: Any mental illness automatically excuses a crime.
Fact: Courts require 'legal insanity' — proof that the person could not understand the nature or wrongness of the act at that specific time, not just a general psychiatric diagnosis.
Myth: Section 84 means the person goes free with no consequences.
Fact: Even if acquitted under Section 84, the person may still be detained under mental health laws for treatment and public safety, not simply released.
Myth: The prosecution must prove the accused was sane.
Fact: Under Section 105 of the Evidence Act, the burden is on the accused to prove unsoundness of mind, not on the prosecution to disprove it.