insanity defense


Insanity has been used as a defence since the time of the Ancient Greeks and Romans. Its existence is from centuries and one of the most famous was the McNaughton case, which leads to the origin of the McNaughton Rule test. This law, made in English Courts, is now followed as a precedent all over the world. The Insanity defence originated from the Latin maxims actus reus non facit reum nisi mens sit rea[1] and furiosi nulla voluntas est[2].

According to Section 84 of the Indian Penal Code, 1860, when a person isn’t in the right mind or is suffering from a mental disease or defect and has no capacity to understand the gravity of the crime or doesn’t know right from wrong, then in such cases, he cannot be held liable for the crime. An accused may use this defence to save himself from punishment where there is no mens rea.

The Insanity defence is important for two reasons. First, for people who suffer because of their own mental health and second, for people misuse this defence to avoid punishment. The burden of proof is extremely severe as it lies entirely upon the accused. It renders this defence one of the most complicated defences in criminal jurisprudence. Practically, it is very difficult to establish whether the accused at the time of committing the crime was of unsound mind or not.

Insanity means when a person is not in the situation to understand what is wrong and what is not or suffering from mental illness which leads to abnormal behaviour. When the person doesn’t know the severity of the act he or she is doing, then it is called insanity. Insanity in legal terms is different from medical science. Insanity in law means a disorder of the mind which impairs cognitive faculty, i.e., the reasoning capacity of a person, to such an extent as to render him/her incapable of understanding the nature and consequences of their action[3].

Every crime must consist of both actus reus[4] and mens rea[5] and when a person doesn’t have any intention to commit an offence then that means the crime isn’t enough to punish a person. When compared to any act of a child, a child still has some sense of right and wrong but a person who is of unsound mind may have no idea about right and wrong. So, to protect such people from punishment the insanity defence was made and an accused can use this defence as an excuse for his or her guilty act.

There are some essential ingredients upon which we analyze and judge the insanity of a person. These are:

  • When a person’s act, who is insane, results in harm.
  • The person doing that act at the time must be suffering from insanity or mental abnormality or unsoundness of mind.
  • The accused person should not have the capacity of knowing the nature of the act committed by him because of insanity.
  • The accused doesn’t possess the ability to understand that the act committed is wrong and what is right or is illegal in nature because of insanity.

According to this defence, the insane person either cannot be held liable for a crime or can be held liable partially for the act which leads to a lesser punishment. The law provides safety of the insane person from their own mind and in fact, a mad man is punished by his own madness, which is the literal meaning of the Latin maxim Furiousus furore sui punier.[6] On the other hand, other people need to be protected from such insane people. So, a provision has been made under Section 330 of the Criminal Procedure Code, 1973 for the detention of such persons in lunatic asylums[7].

Insanity is of multiple types which results in derangement of the mind. For example, if a person is suffering from Schizophrenia then he/she might be hallucinating which may lead him or her to act in a wrong way without knowing about it. In Ashiruddin v. The King[8], the accused killed his five-year-old son with a knife because of an illusion that he was sacrificing his son because he thought that he was commanded by someone from paradise to sacrifice his child. So, he took his son to the mosque and cut his neck with the knife while believing it to be a dream. The Calcutta High Court allowed the defence of Insanity under Section 84 of Indian Penal Code, 1860 because of the essential ingredient of the act that he committed was not known by him whether it is right or wrong[9], was fulfilled.

Such illusions, disorders, etc. lead to the commission of crimes that have no mens rea. Thus this law may be said to be made to protect a person from himself. This section has been an introduction to the protection of a person from their own insane mind because it’s not the fault of the person suffering from illness.

The most significant inquiry that emerges then, is how it’s to be detected and what ought to be the differentiating line among ‘sanity’ and ‘insanity’ to expand a man the indictment of law from criminal prosecution?[10] There are many types of tests that can determine if a person who is committing a crime is of unsound mind at the time of the act.

  1. McNaughton Rule Test:

This is the most famous and the first case which was introduced, R v. McNaughton (1843)[11].11 In this case, the accused was in the delusion that the then Prime Minister of England Sir Robert Peel hurt him or injured him. So, he wanted to kill him to save himself. Instead, Prime Minister’s secretary Edward Drummond was shot dead by the accused on January 20, 1843, as he thought that Edward was Sir Robert Peel. The Court allowed the defence of insanity through five questionnaires which were asked by 15 Judges of The House of Lords for clearing the view on the subject.

The House of Lords then gave the following dicta: Every man is to be presumed to be sane, and that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from the disease of the mind, and not to basically nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong. So, in order to declare a person insane legally, he should meet the criteria that he does not know what he is doing and what the act means and cannot differentiate between right or wrong.”[12]

  1. The “Irresistible Impulse” Test:

It tests whether the accused is capable of resisting the impulse to commit the act or not i.e. whether a person has no control over his actions, even while knowing the act is wrongful in nature and is compelled to do an offence which is contrary to law. This test can be best used in testing manias and paraphilias[13]. So, the accused pleads not-guilty by giving the reason that he has no control over himself. Giving punishment to such a person who has committed the offence without any intentions is odd. We can say that many people in asylums are in a condition where they know about right and wrong but cannot control themselves.

  1. The Durham Rule (The “Product” Test):

We can say that this rule developed the way of researching insanity as a test and gave a better understanding and better results. Unlike the McNaughton rule, it is more specific in nature as it approaches the determination of insanity in a more scientific and psychological method. The name of the test is derived from the name of a man named Monte Durham. He was a 23-year-old who used to come in and out from prison and medical institutions. The investigators said that he was suspected of breaking in and some other criminal act. It was difficult to identify his illness by old methods of analysis. This rule was introduced for developing future insanity tests that would help in determining cases of insanity.

  1. Model Penal Code Test:

This test was published in America which is the mixture of McNaughton rule and Durham’s rule. This test helps in knowing the cognitive functioning of the brain and helps where the accused was legally insane at the time of the crime or not. So, these are the different tests which with the help of psychologist and psychiatrist are used in insanity analysis.

Medical insanity is different from legal insanity. By medical insanity, it means the capacity which a person’s consciousness can take the burden of the act he has done, and others affected by him while legal insanity means what is the relation of the person’s mind or consciousness to himself.[14] In medical terms, insanity affects the person in many ways like their cognitive functioning, intellectual faculties, and overall personality. In legal terms, the main objective of the law is to see the consequences of the act done by the insane person. If a person is suffering from any mental illness that doesn’t mean he cannot be held liable for a crime. In law, insanity can be used as a defence only when the person is in that state of mind during the commission of the act such that there can be no question of the existence of men’s rea.

In wider connotation, it constitutes retardation, madness, lunacy, mental derangement, disturbance, and each different types of abnormality best known to medical science[15] and “all kinds of insanity are not recognized by law.[16]” The courts look for the existence of legal insanity and not medical insanity like in the case Surendra Mishra v. State of Jharkhand[17], the Supreme Court held that the court wants legal insanity as proof and not medical insanity which is under Section 84 of Indian Penal Code. The accused pleaded not guilty for the murder of the victim.

The court says that the accused is merely conceited, odd and if his brain is not in the right state or if the mental or physical ailments from which he suffered have rendered his intellectual abilities and attacked his emotions or if he indulges in certain unusual acts, or has fits of insanity or short intervals or if he was suffering from epileptic fits and there was abnormal behaviour at times, all these instances are not enough to consider the accused’s appeal. So, the above case states that only medical insanity isn’t sufficient as a plea for an insanity defence.

A person is always presumed to be sane under the law until it’s proven that a person has done something which is contrary to law. It is upon the judge to decide whether a person is responsible for his or act acts unless the contrary is proved.[18] When the situation occurs that the accused must prove his legal insanity, then that means the accused has done the crime and he has accepted it. In Anandrao Bhosle v. the State of Maharashtra,[19] the husband killed his wife and had a family history of psychiatric illness and was suffering from Schizophrenia and the court held that the burden of proof lies on the accused party who wants the advantage of Section 84 of Indian Penal Code, 1860 and the person should be of unsound mind while committing the crime.

So, it depends on the defendant how to prove the legal insanity by hiring a psychologist and justifying about the series of events which shows that the person was of unsound mind. The court also hires a psychologist or psychiatrist to verify the insanity of the person. Secondly, it depends on the judge to decide whether the person is legally insane or not.


As of now, we can agree that Insanity Defence has become a loophole for the criminals as the most popular defence to discharge from any crime. It is next to impossible to demonstrate the psychological position of any person at the time when the crime was committed. The redundancy of Indian Judicial System is also to be held responsible here because it simply adds fuel to the fire which makes this defence lose its stark, and all that matters are word-games. These cases are more complicated than any other case because here an accused agrees to the commission of a crime but evades the consequences and this raises brows of any right-minded person. People should not feel pain because of some people that take advantage of the law. As Sir Blackstone once said better that ten guilty persons escape than that one innocent suffers.[20]

For these fundamental reasons it could safely be concluded that Insanity Defence Law has lost its original zeal and has now become a tool for criminals to evade legal consequences. Now the remedies available to cope up with these lacunas are the formation of more straightforward laws and tests. The preliminary step towards improvements could be a mechanism to differentiate between Violent criminals and Insane criminals, wherein the former are the real culprits. Reforms here can only be possible when states would make stricter laws to govern such matters and it is high time now for major reforms in these provisions.


ayush shaw Ayush Shaw | Kolkata


[1] An act doesn’t constitute guilt unless done with a guilty intention.

[2] A person with mental illness has no free will.

[3] K D Gaur, Textbook on Indian Penal Code, sixth edition 207 (Universal Law Publishing Lexis Nexis, 14th floor, building no. 10, Tower B, DLF Cyber City, Phase-II, Gurugram, Haryana, India, 2016).

[4] action or conduct which is a constituent element of a crime, as opposed to the mental state of the accused

[5] the intention or knowledge of wrongdoing that constitutes part of a crime, as opposed to the action, or conduct of the accused.

[6] K D Gaur, Textbook on Indian Penal Code, sixth edition 206 (Universal Law Publishing Lexis Nexis, 14th floor, building no. 10, Tower B, DLF Cyber City, Phase-II, Gurugram, Haryana, India, 2016).

[7] Ibid 207

[8] AIR 1949 Cal. 182

[9] K D Gaur, Textbook on Indian Penal Code, sixth edition 210 (Universal Law Publishing Lexis Nexis, 14th floor, building no. 10, Tower B, DLF Cyber City, Phase-II, Gurugram, Haryana, India, 2016).

[10] Ibid 207

[11] 8 ER 718, Volume

[12] Available at: (last visited on May 8, 2020; 15:24

[13] Available at: (last visited on 13 July, 2020; 18:49)

[14] The British Royal Commission Report, 1953 para.229

[15] Eshita, “Insanity Defence: Medical and Legal Grapple, Vol:2, Page: 6; Available at (last visited at 12 July 2020; 15:20)

[16] Bharat Kumar v. State of Kerala, (2010) 10 SCC 582.

[17] AIR 2011 11 SCC 495

[18] Insanity defence: A loophole for criminals; Available at (last modified at 12 March 2020).

[19] AIR 2002 SCC 219.

[20] Sir Blackstone, “Commentaries on the laws of England” J.B. Lippincott Co., Philadelphia, 1893.


Please enter your comment!
Please enter your name here