This article is written by Khushi Agrawal, from Symbiosis Law School, Noida, and Mahima Mishra, from Vivekananda Institute of Professional Studies.


There is a well-established principle, “Actus Non Facit Reum Nisi Mens Sit Rea,” which, in the literal sense means, an act does not make an offender liable without a guilty mind. The Intention or guilty mind (Mens Rea) of the offender is an integral part while committing a crime. The defence of insanity is a law that protects a person who is incapable of understanding the nature of the act done by him. 

The unsoundness of mind should be of such an extent that it makes the offender completely incompetent in knowing the nature of the act. The factor that the person is suffering from a mental illness is by itself not sufficient to prove that he is insane. Under Indian law, the rationale of insanity as a defence is incorporated in Section 84 of the Indian Penal Code, 1860, and is based upon the “Mc’Naughten’s Rule.” The burden of proof is always on the defendant, and it has to be proved beyond a reasonable doubt.  The Law Commission of India in its 42nd report, made an effort to reanalyze Section 84, but no modifications were made.

Origin of the Rules on the Plea of Insanity

The insanity law as a defense has been in existence from many centuries. But, it took a legal status from the last three centuries. The history of the law of insanity can be traced back to the 1700s. 

The first case which dealt with the law of insanity was R v. Arnold (1724), in which Edward Arnold attempted to kill and even wound Lord Onslow and was tried for the same. The evidence clearly showed that the accused was suffering from a mental disorder. Tracy, J. observed:

“If he was under the visitation of God and could not distinguish between good and evil, and did not know what he did, though he committed the greatest offence, yet he could not be guilty of any offence against any law whatsoever.”

As stated in the aforementioned case, a person can demand immunity if, due to his unsoundness of mind, he was incapable of distinguishing between good and evil and did not know the nature of the act committed by him. This test is known as the “Wild Beast Test.”

The second test evolved in Hadfield’s case (1800). Hadfield was discharged from the army on the ground of insanity and was tried for high treason in attempting to assassinate King George III. The counsel of the accused, Lord Thomas Erskine, defended him and proved in front of the judge that Hadfield only pretended to kill the King and is not guilty, on the ground of insane delusion from which the accused was suffering.

Erskine stated that insanity was to be determined by the fact of fixed insane delusion and that such delusion under which the defendant acted is the main reason for his crime. This test was known as the “Insane Delusion Test.”

Finally, the third test was formulated in Bowler’s case (1812). In this case, Le Blanc, J. stated that the jury has to decide when the accused committed the offence, whether he was capable of distinguishing right from wrong or under the control of an illusion. After the Bowler’s case, the courts have placed more emphasis on the capacity of the accused to distinguish right from wrong, though the test was not that clear. 

Mc’Naughten’s Rule

There have been several tests from time to time, like the Wild Beast Test, Insane Delusion Test, etc. But the most important is the “Right and Wrong Test” formulated in M’Naughten’s case.

The hearing of M’Naughten and his release was a topic of discussion in House of Lords, and as a consequence, they called upon fifteen judges to decide on the question of criminal liability in the cases where the accused is incapable of understanding the nature of the act and also answered the questions advanced. Fourteen judges had the same answers. The view of the majority was given by Tindal C.J., these answers to the questions are known as M’Naughten’s Rule. The following principles were cited:

  1. If the person knew what he was doing or was only under a partial delusion, then he is punishable.
  2. There is an assumption that every man is prudent or sane and knows what he is doing and is responsible for the same. 
  3. To establish a defense based on insanity, it must be ascertained, at the time of perpetrating the act, the accused was in such a state of mind as was unable to know the nature of the act committed by him.
  4. A person who has sufficient medical knowledge, or is a medical man and is familiar with the disease of insanity cannot be asked to give his opinion because it is for the jury to determine, and decide upon the questions.

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.
                 Click Above

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.

Irresistible Impulse as a defence

Irresistible impulse is a sort of insanity where the person is unable to control his actions even if he has the understanding that the act is wrong. In some cases, the Irresistible Impulse Test was considered to be a variation of Mc’Naughten’s rule; in others, it was recognized to be a separate test. Though the Irresistible Impulse Test was deemed to be an essential corrective on Mc’Naughten’s selective perception, it still had some criticisms of its own.

Under English Law

In 1884, the irresistible impulse test was introduced by the legislation. By 1967, this test was applicable in 18 states out of 51 states of the U.S.A.  Irresistible impulse when, attributable to a diseased mind, appears to have been identified as a legitimate excuse in some English cases.

Irresistible impulse as a defence was developed in the famous case of Lorena Bobbit (1993), on June 23rd, 1993, the defendant took a knife from her kitchen and wounded her husband by cutting off his penis while he was sleeping. Her lawyers contended that she had been suffering from domestic violence, which was perpetrated by her husband during her marriage, and his husband even raped her before she committed this act. Though she was well aware of the consequences, she was not able to control her actions and demanded that she was subject to an irresistible impulse. The state of Virginia was the first state which used this defence in its original form. It was held that she’s not guilty as she was suffering from temporary insanity. 

Under Indian Law

Usually, when there is adequate capacity to distinguish between right and wrong, the mere presence of an irresistible impulse would not excuse liability. Irresistible impulse is not incorporated under insanity because it does not fall within the ambit of Section 84 of the Indian Penal Code.

In the case of, Kannakunnummal Ammed Koya v. State of Kerala (1967), it was held that to claim an exemption under section 84, the insanity has to be proved, at the time of the commission of an act, mere losing of self-control due to excitement or irresistible impulse provides no defence under Indian law even if this is proved in a court of law.

In another case, Ganesh v. Shrawan (1969), it was observed that the mere fact that the murder is committed by the accused on an irresistible impulse, and there is no identifiable motive for the commission of the act, can form no grounds for accepting the defence of insanity.

Durham Rule

The Durham defence is also known as the “Durham rule,” or the “product test” was established in the case of, Durham v. United States (1954), the defendant was guilty of breaking into a house and demanded the plea of insanity in his defence. The existing tests, which were the Mc’Naughten Rule and the irresistible impulse test, were declared to be obsolete by the Court of Appeal. But later on, it was understood that both these tests could still be employed, and the Durham rule can be used in addition to these tests.

This defence has two main components: 

  1. First, the defendant must possess a mental disease or infirmity. Although these words are not explicitly explained in the Durham case, the language of the judicial view indicates an effort to rely more on objective, psychological standards, rather than focusing on the defendant’s subjective cognition. 
  2. The second element has to do with causation. If criminal behavior is “caused” by the mental disease or defect, then the conduct should be exempted under the circumstances. 

This test is currently accepted only in New Hampshire, considering it has been regarded too broad by other jurisdictions.

Concept of Diminished Responsibility

The Doctrine of Diminished Responsibility was introduced by the Homicide Act of 1957, as a defence to murder. If this defence is established, it will entitle the offender to be found guilty of manslaughter (culpable homicide) instead of murder. 

Section 2 of the Act clearly states that:

  1. Where a person kills someone or is a party to killing, he will not be guilty of murder if he was suffering from some abnormality of mind and is mentally incapable of taking responsibility for his acts.
  2. A person who would be liable under this section, whether as a principal or as an accessory, will be convicted of manslaughter instead of being convicted of murder.

Leading Indian Cases

Ratan Lal v. State of Madhya Pradesh

The appellant was caught setting fire to the grass in an open land of Nemichand, when he was asked why he did it, he replied; ‘I burnt it, do whatever you want.’ The appellant was charged under Section 435 (mischief by fire with intent to cause damage) of the Indian Penal Code. According to the psychiatrist, he was a lunatic in terms of the Indian Lunacy Act, 1912. The report explicitly stated that the accused is:

  1. Remains depressed,
  2. Doesn’t speak,
  3. He is a case of lunatic depression and psychosis, and
  4. He requires therapy.

The trial court held that the accused was not liable to be punished. An appeal was filed by the state, and the High court reversed the findings of the trial and held the accused liable for the offence. Afterward, the Supreme Court allowed the appeal, and the conviction was set aside based upon two major factors:

  1. Medical evidence provided and, 
  2. According to the behavior of the accused on the day of the occurrence.

These factors indicated that the accused was insane within the meaning of Section 84, IPC.

Seralli Wali Mohammad v. State of Maharashtra

The offender was charged under Section 302 of the Indian Penal Code for causing the death of his wife and daughter with a chopper. The Supreme Court rejected the plea of insanity because the mere fact that there was no motive proved, or that he did not attempt to run, was not sufficient enough to prove that he did not have the mens rea for committing the act. 

Shrikant Anandrao Bhosale v. State of Maharashtra

In this case, the accused was a police constable. The wife was hit on the head with a grinding stone by the accused, and she was immediately taken to the hospital but was found already dead. After investigation, the appellant was charged for the offence of murder. Insanity was pleaded as a defence. The appellant had a family history where his father also suffered from mental illness. The reason for such an ailment was not known. The appellant was undergoing treatment for this mental disease. It was observed that the motive for the murder was quite weak. After killing his wife, the accused did not attempt to hide or run away.

Based on the above-stated facts, it was held that the accused was suffering from paranoid schizophrenia, and he was incapable of comprehending the nature of the act committed by him. Therefore he was not guilty of murder and will be given the benefit of section 84, IPC.  

Jai Lal v. Delhi Administration

Here, the appellant killed a small girl with a knife and even stabbed two other people, was convicted under Section 302 of the Indian Penal Code. It was pleaded by the accused that he was suffering from insanity within the ambit of Section 84, IPC. 

It was observed that the accused, after being arrested gave normal and intelligent statements to the investigating officers. Nothing abnormal was noticed in his behavior. Considering all these findings, the Supreme Court held that the appellant was not insane at the time of the commission of the act and was well-aware of the consequences of his acts. He was held guilty for murder under Section 302, IPC.

Misuse of Insanity as a Defence

In the present scenario, there are very high chances that the defence of insanity can be very well abused as it is a very strong weapon to escape the charges of an offence. It is impossible to prove that the person was incapable of understanding the nature of the act. Defence lawyers can use it to free the culprits of intentional unlawful acts. 

Here the courts play an important rule as they have to make sure that a sane person doesn’t absolve himself by wrongfully using the defence in his favour. In many jurisdictions, this defence has been abolished completely, e.g., Germany, Thailand, Argentina, etc. 


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

LawSikho has created a telegram group for exchanging legal knowledge, referrals and various opportunities. You can click on this link and join:

Follow us on Instagram and subscribe to our YouTube channel for more amazing legal content.

Did you find this blog post helpful? Subscribe so that you never miss another post! Just complete this form…