General Exceptions: Insanity


Indian Penal Code, 1860 is a part of Criminal Law which consists of mens rea and actus rea.

The General Exceptions talk about the absence of mens rea i.e. guilty mind which have been prescribed in Chapter IV of the Code. General exceptions can be classified into excusable and justified defences.

1. Excusable Defences

  • Mistake (S. 76 & 79)
  • Accident (S. 80)
  • Infancy (S. 82 & 83)
  • Insanity (S. 84)
  • Intoxication (S. 85 & 86)

2. Justified Defences

  • Judicial Acts (S. 77 & 78)
  • Necessity (S. 81)
  • Consent (S. 87-89 & 92)
  • Communication (S. 93)
  • Trifle Acts (S. 95)
  • Duress (S. 94)
  • Private Defence (S. 96- 106) 

Insanity as under Chapter IV

Sec. 84 states for any to not be an offence if the act is done by a person who at the time of doing the act cannot ascertain the nature or degree of act done or that the act is in itself unlawful due to unsoundness of mind.

To hold any person responsible for any crime committed, it is essential for there to exist criminal intention. Sir James Stephen has observed, that no act can be criminal if the person who commits the said act has defective mental power or any disease which affects his mind from knowing the nature or quality of the act or the knowledge that the act is wrong.

The ingredients of S.84 are;

1. The person must be of unsound mind

2. The person must be incapable of ascertaining

a. Nature of the act

b. Act was contrary to law

c. Act was wrongful

3. The reason of such incapacity must be unsoundness of mind

Illustration:A is of unsound mind. Not understanding the nature and degree of his act, attempts to steal; A is guilty of nooffence.

Case: R v. Arnold (1724) 16 St. Tr. 695

The accused was tried for attempting to kill and wound the person. Enough evidence of the mental derangement of the accused existed. Justice Tracy in this case held the accused not guilty and laid down a test which stated that if he could not distinguish between good and evil and can not determine what he did, he will not be guilty of the offence committed even though the offence may be the greatest offence.  

Case: Shriram v. State of Maharashtra 1991 Cri. LJ 1631 (Bom.)

The accused killed his three granddaughters who were infants with the handle of a grinding stone and further did not conceal the bodies of the victims nor attempted to evade the law, it was found he made no preparation of the killing as well. It was pleaded that the accused was not of sound mind at the time of committing the act. It was held that there existed no mensrea as the accused killed the children in fits of lunacy.

Types of Persons of Unsound Mind


A person of non-sane memory from birth due to a perpetual infirmity with any lucid intervals can be said to be an idiot.


A lunatic is a person who is affected by any mental disorder only at certain vicissitudes and periods and has intervals of reason.

Non Compos Mentis

A person is made non compos mentis by a illness.

Burden of Proof

The burden of proof like all the other defences under Chapter IV lie on the accused. The defence of insanity cannot be merely be granted on the circumstances or character of crime. There needs to be proof of legal insanity at the time of commission of the crime. Every insanity recognised by medical science may not necessarily be legal inanity.

Frequently Asked Questions

1. Is insanity caused by drunkenness valid?

Drunkenness cannot be said to be an excuse but if insanity caused by drinking causes such a degree of madness that it renders a person incapable of distinguishing from right and wrong can by the discretion of the court be an exemption from the liability. 

2. What is legal insanity?

In order to avail the defence under S.84, it is important for the defendant to prove legal insanity. It must be proved that at the time of commission of the act, such insanity existed and the person did not know the gravity and nature of the act.

3. Is irresistible impulse by an insane person covered under this section?

Irresistible urge when combined with a diseased mind has been accepted as a valid excuse under the English law.

4. An involuntary act by an insane person?

Even a voluntary act by an insane person is excusable, any involuntary act committed by an insane person where he or she is incapable of knowing the degree and nature of the act will also be excusable.

5. Relevance of insanity at the time of commission of act?

It is relevant. As his state of mind, whether sound or unsound, has a direct effect on the criminal intention (mens rea) of the act. It is necessary to prove insanity at the time of commission of the act.

Edited by Shikhar Shrivastava

Approved & Published – Sakshi Raje 


1. R v. Arnold ,(1724) 16 St. Tr. 695

2. Shriram v. State of Maharashtra ,1991 Cri. LJ 1631 (Bom.)

3. S.N. Misra, Indian Penal Code, 167-179, (20th ED. 2016) Central Law Publications, Allahabad. 

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