This article is written by Khushi Agrawal, a student of Symbiosis Law School, Noida. In this article, she has discussed the concepts of insanity as a defence under IPC in detail.


In India, Section 84 of IPC describes the defences available to the person of an unsound mind. Persons of unsound minds are vulnerable in nature. There is a complete chance of their exploitation in a situation where they are not being sought protection. The law that protects an unsound minded person and provides defence from criminal liability to the unsound minded person is known as the Law of Insanity. Whenever an insane person commits a crime due to the effect of his insanity, he does not have a guilty mind to understand that what he is doing is something that is prohibited by law. The insanity law has proven to be of practical importance in understanding the situation and the mental position of an insane person and in certain reasonable circumstances granted them exemption from criminal liability.

Origin of the Rules on the Plea of Insanity

According to the rule of the M’Naghten, it must be clearly demonstrated, in order to establish the defence of insanity, that the accused worked under a fault at the time of the act so much as to be unaware of the nature and quality of the act he was doing. This explanation cannot be taken as a full definition of proof, as it fails to explain various aspects of insanity.

It is therefore imperative to note that the term “insanity” has a particular meaning in criminal law. It is not necessarily used in its medical sense, but its legal significance must be understood. Therefore,  insanity as a defence refers to legal insanity and not medical insanity. The concept of ‘legal insanity’ refers to certain requirements to be met by the accused according to the rules laid down in the law. Legal insanity is a narrower concept than medical insanity.  Legal insanity is a concept narrower than medical insanity. For example, some mental illnesses such as schizophrenia, paranoia or lunacy may overlap with the legal and medical conceptions of insanity and may also be protected against insanity or insanity of mind when the other conditions are fulfilled in order to satisfy legal insanity criteria.

English Law on the Defence of Insanity

English criminal law considers insanity a valid defence of crime. The fundamental definition of insanity is based on the M’Naghten Rules. These rules are not about insanity medical definitions. In M’Naghten’s case, the judges declared the following insanity principles:

  1. All are presumed to be sane and to have enough reason, until proved contrary, to be responsible for their crimes.
  2. It must be clearly demonstrated in order to establish the defence of insanity that at the time of the act, the accused was working under such a defect of reason, from mental illness, as
  3. He didn’t know the nature and the qualities of the act he was doing or
  4. He did not know what he was doing was wrong.

The accused must, therefore, prove on the basis of the facts that he was suffering from a defect of reason caused by mental illness in an effort to argue insanity, because either he was unaware of the nature and quality of the act, or he had not realized that his actions were wrong.


Indian Law on the Defence of Insanity

Insanity is provided in accordance with Section 84 of the Indian Penal Code as a defence under Indian Law. However, the term “insanity” is not used under this provision. The Indian Penal Code uses the sentence “mental soundness.” In accordance with the code, the defence of insanity, or that can also be called defence of mental insanity, comes from M’Naghten’s rule.

In Section 84 of the Indian Penal Code, a person of an unsound mind shall act- Nothing is an offence committed by someone who is currently unable to know the nature of the act or does what is wrong or contrary to legislation due to a lack of a sound mind.

Nevertheless, it should be noted that the framers of the IPC preferred to use the expression “insanity of mind” instead of the term “insanity.” Insanity’s scope is very limited, while the mind’s insanity covers a large area.

For this defence, the following elements are to be established-

  1. The accused was in a state of unsoundness of mind at the time of the act.
  2. He was unable to know the nature of the act or do what was either wrong or contrary to the law. The term ‘wrong’ is different from the term ‘contrary to the law.’

If anything is ‘wrong’, it is not necessary that it would also be ‘contrary to the law.’ The legal conception of insanity differs significantly from medical conception. Not every form of insanity or madness is recognized as a sufficient excuse by law.

Distinction between Legal and Medical Insanity

Section 84 of the Indian Penal Code sets out the legal responsibility test as distinguished from the medical test. It can be observed that the absence of will arises not only from the absence of understanding maturity but also from a morbid state of mind. This morbid mind condition, which provides an exemption from criminal responsibility, differs from the medical and legal point of view. According to the medical point of view, it is probably correct to say that every person, when committing a criminal act, is insane and therefore needs an exemption from criminal responsibility; while it is a legal point of view, a person must be held to be the same as long as he is able to distinguish between right and wrong; as long as he knows that the act carried out is contrary to the law.

It has been ruled by the Supreme Court that “mentally ill” people and psychopaths are unable to seek immunity from a criminal case, as it is their responsibility to demonstrate insanity at the time the crime was committed. So in practice, not every person who is mentally ill is exempt from criminal liability. There has to be a distinction between legal insanity and medical insanity. “Arijit Pasayat and the Bench of Justices, DK Jain, stated while upholding the life conviction of a man who cut off his wife’s head. The mere abnormality of mind, partial delusion, irresistible impulse or compulsive behavior of a psychopath does not provide protection from criminal prosecution as provided by the apex court held Section 84 of the Indian Penal Code (IPC). The Bench stated that Section 84 of the IPC, which provides immunity from criminal prosecution to persons of unsound mind, would not be available to an accused, as the burden of proving insanity would lie with them, as provided in Section 105 of the Indian Evidence.

In the case of Hari Singh Gond v. State of Madhya Pradesh[1], the Supreme Court observed that Section 84 sets out the legal test of responsibility in cases of alleged mental insanity. There is no definition of ‘mind soundness’ in IPC. However, the courts have mainly treated this expression as equivalent to insanity. But the term ‘insanity’ itself does not have a precise definition. It is a term used to describe various degrees of mental disorder. So, every mentally ill person is not ipso facto exempt from criminal responsibility. A distinction must be made between legal insanity and medical insanity. A court is concerned with legal insanity, not medical insanity.

In the case of Surendra Mishra v. State of Jharkhand[2], It was pointed out that ‘every person suffering from mental illness is not ipso facto exempt from criminal liability.’ Furthermore, in the case of Shrikant Anandrao Bhosale v. State of Maharashtra[3], the Supreme Court, in determining the offense under Section 84 of the IPC, held that’ it is the totality of the circumstances seen in the light of the recorded evidence’ that would prove that the offense was committed.’ It was added: “The unsoundness of the mind before and after the incident is a relevant fact.”

Unsoundness of mind must be at the time of the commission of the Act.

The first thing a court to be considered when defending insanity is whether the accused has established that he was unsound at the time of committing the act. The word “insanity” is not used in Section 84 of the penal code.

In Rattan Lal v. State of M.P[4], it was well established by the court that the crucial point of time at which the unsound mind should be established is the time when the crime is actually committed and whether the accused was in such a state of mind as to be entitled to benefit from Section 84 can only be determined from the circumstances that preceded, attended and followed the crime. In other words, it is the behavior precedent, attendant and subsequent to the event that may be relevant in determining the mental condition of the accused at the time of the commission of the offense but not those remote in time.

In Kamala Bhuniya v. West Bengal State, the accused was tried for her husband’s murder with an axis. A suit was filed against the accused, she alleged to be insane at the time of the incident, the investigating officer recorded at the initial stage about the accused’s mental insanity. The prosecution’s duty was to arrange for the accused’s medical examination, it was held that there was no motive for murder. The accused made no attempt to flee, nor made any attempt to remove the incriminating weapon Failure on the part of the prosecution was to discharge his initial responsibility for the presence of mens-rea in the accused at the time of the commission of the offence. The accused was entitled to benefit from Section 84. And hence accused was proved insane at the time of the commission of the offence and was held guilty of Culpable Homicide and not of Murder.

Incapacity to know the nature of the act

The word “incapacity to know the nature of the act” embodied in Section 84 of the Indian Penal Code refers to that state of mind when the accused was unable to appreciate the effects of his conduct. It would mean that the accused is insane in every possible sense of the word, and such insanity must sweep away his ability to appreciate the physical effects of his acts.

Incapacity to know right or wrong

In order to use the defence of insanity under the latter part of Section 84, namely “or to do what is either wrong or contrary to the law,” it is not necessary that the accused should be completely insane, his reason should not be completely insane, his reason should not be completely extinguished. What is required, is to establish that although the accused knew the physical effects of his act, he was unable to know that he was doing what was either “wrong” or “contrary to the law.” This part of Section 84 has made a new contribution to criminal law by introducing the concept of partial insanity as a defence against criminal insanity. However, as a practical matter, there would probably be very few cases in which insanity is pleaded in defence of a crime in which the distinction between “moral” and “legal” error would be necessary. In any crime, insanity can undoubtedly be pleaded as a defence, yet it is rarely pleaded except in murder cases. Therefore, in a case, this fine distinction may not be very useful for the decision. The Indian penal code has advisably used either “wrong or contrary to the law” in Section 84, perhaps anticipating the controversy.


It is suggested that there should be a well-defined definition of the term ‘mental insanity’ to avoid the various controversies and confusions that arise in understanding and differentiating between the ‘mental disease’ and the actual insanity of mind sought by the Code or the so-called ‘legal insanity’ in order to make the defence available to the accused.

Section 84 of the Code should be amended to incorporate the partial defence of diminished responsibility for murdering insane persons. This change shall be made on an equal footing with the defence of diminished responsibility as accepted under the defence of insanity as specified by English criminal law.

The scope of Section 84 should be expanded to incorporate the defence of automatism under the defence of an unhealthy mind, just as it is recognized by the English criminal law system.


  1. (2008) 16 SCC 109
  2. (2011) 11 SCC 495
  3. (2002) 7 SCC 748
  4. JT 2002 (7) SC 627


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