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Understanding the insanity defense under Indian law

Read this article to learn concepts and the procedure of raising an insanity claim under Indian law.
© Project 39A, National Law University Delhi


Section 84 of the Indian Penal Code, 1860 (IPC) provides for the defense of insanity, and is one of the general defenses available under the IPC. Derived from the M’Naghten Rule, the defense under section 84 states that a person who at the time of commission of the offence was of unsound mind, is exempt if they didn’t know the nature of the act or its consequences.

Overview of the insanity defense

The defense under s.84 has two requirements and both must be met.

-unsoundness of mind at the time of the commission of the offence (‘medical insanity’); and

-by reason of this unsoundness of mind, the person was incapable of knowing the nature of the act or that it was either wrong or contrary to law (‘legal insanity’).

The second limb requires the defendant to satisfy any one of the three incapacities-

  1. the person did not know the nature of the act (cognitive incapacity); or
  2. even if the person knows the nature of the act, they do not know that the act is morally wrong; or
  3. even if the person knows the nature of the act, they do not know that the act is contrary to law.

Once medical insanity has been established, courts look at the ‘totality of circumstances’ to determine legal insanity and whether the requisite threshold for a successful defense has been met. However, an active inquiry into legal insanity is rarely undertaken. Instead, often courts infer legal insanity based on a host of factors, including the nature of the mental illness, (lack of) motive and behaviour of the accused before, during and after the act.

Unsoundness of mind at the time of the commission of the offence

The term unsoundness of mind is undefined under the IPC. Various terms like ‘lunatic’, ‘loss of mental equilibrium’, ‘madman’, ‘idiot’ and ‘insane’ have been used synonymously, providing no clear direction towards understanding the term (Read Bapu v. State of Rajasthan (2007) 8 SCC 66). Unsoundness of mind must be present at the time of the commission of the offense. Currently, there is no standardised procedure followed by psychiatrists in making a determination of a person’s mental condition at the time of the offence. In the absence of prior records of the accused’s undetected mental illness, psychiatrists have little material to rely on, and may not have access to key witnesses in the life of the accused to fill in the gap.

Incapacity to know the nature or consequences of the act

Indian jurisprudence is unclear and inconsistent on the degree of incapacity that is required under s.84. In Queen-Empress v. Kader Nasyer (1896) ILR 23 the court held that unsoundness of mind which ‘materially impairs’ the cognitive faculties of the mind forms a ground of exemption from criminal responsibility. On the other hand, the court in Lakshmi v. State (1958) SCC OnLine All 208, required complete extinguishment of the ability to know the nature or consequences. In other words, varying degrees of incapacity have been held sufficient under the second limb.

Totality of Circumstances Framework

Courts look at surrounding circumstances to infer legal insanity. Some of these circumstances are the history of mental illness, lack of motive/weak motive, treatment post-arrest, behaviour on the day of the incident and subsequent conduct of the accused. While courts are unanimous in the relevance of inquiring into surrounding circumstances, they are inconsistent in determining the relevance and weightage of these circumstances.

Evidentiary requirements

A reading of s.105 with s.3 of the IEA makes it evident that the standard of proof required is that of the preponderance of probabilities. In effect, the accused has to establish, on a preponderance of probabilities, that they were of unsound mind at the time of offence because of which they were incapable of knowing the nature or consequence of their actions. In other words, it is not enough to make a mere claim of insanity, the defense must be able to prove on a preponderance of probabilities that the accused was legally insane at the time of the commission of the offence.


While the wording of s.84 is seemingly straightforward, s.84 jurisprudence is not consistent. Courts have assigned different meanings to what it means to successfully raise a s.84 defense. There are stark differences in the required mental state, the relevant time period of that mental state and the manner in which that mental state is to be established. Differences in each of those aspects then bring to bear a different burden on the person seeking to invoke the s.84 defense.

© Project 39A, National Law University Delhi
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Forensic Mental Health and Criminal Justice

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