Understanding the ‘defense of insanity’

The insanity defense is a defense by excuse, as opposed to defense by justification, in a criminal case wherein the defendant has to prove that he/she is not liable for committing the crime, for which they have been accused, by reason of “insanity”. It is based on the assumption that at the time of committing the crime, the defendant was in a state of “insanity or lunacy”, or suffering from a mental illness, due to which he/she was incapable of appreciating the true nature of the crime and its consequences thereafter.

Hence, they cannot be held legally accountable for committing the crime. Say, for example, a person has/suffers from a persistent mental disorder due to which he has fits of rage. During one such episode, he ends up thrashing his friend to death. In such a case, he can plea the defense of insanity and can be exempted from undergoing punishment for the crime.

Insanity in legal terms

The insanity defense is a legal concept and not a clinical (medical) one. This means that just suffering from a mental disorder is not enough to prove insanity. The defendant has the burden of proving the defense of insanity by a “preponderance of the evidence”, which means that the defendant must prove that he/she was in a state of “insanity” at the time of the commission of the act (legal insanity) beyond a reasonable doubt, and hence cannot be held liable for committing the act. But it is hard to prove legal insanity in court, and it is even harder to defend it. This is because of the requirements to be met by the defendant as per rules laid down by law in order to successfully invoke the defense of insanity.

This issue has been subject to controversy from the very beginning and has raised many debates among medical, psychology, and law professionals all over the world. In this article, we will mainly focus on the overall outlook of the insanity defense under Indian and English law and its loopholes.

Let us first look at the origin and history of this law.

Origin and history of ‘insanity defense’

The concept of defense by insanity is centuries old and has existed since ancient Greece and Rome. A clause regarding the insanity defense was first recorded in 1581 in an English Legal Treatise which stated that “A lunatic, if at the time of his lunacy, kills someone, then that person cannot be held accountable for their actions.” It was in late 13th century England, that the common-law courts first recognized “Complete Madness” as a defense against criminal charges.

By the 18th century, this evolved into the “wild beast” test under which the English Common Law deemed that an insane person had the mental capacity of a “wild beast” (in the sense, a dumb animal). Under this test, the defense of insanity could be availed by a person who was “totally deprived of his understanding and memory so as not to know what he was doing no more than an infant, a brute, or a wild beast”.

M’Naghten case

The 1843 M’Naghten case[1] in Britain became a legendary precedent in law with regards to the defense of insanity. In this case, Daniel M’Naghten, a wood-turner from Glasgow, was acquitted for the murder of Edward Drummond, the secretary of the British Prime Minister, whom he mistook for the British Prime Minister Robert Peel believing that there was a conspiracy against him involving the government. He was declared insane by the high court and hospitalized in Bethlem Hospital. This case led to the development of the M’Naghten Standard which states that “ at the time of committing the act, the party accused was laboring under such a defect of reason, from a disease of the mind, as to not know the nature and the quality of the act that he was doing, or as not to know that what he was doing was wrong”. So essentially, the elements of this act are:

  1. Firstly, a person must have a mental illness.
  2. Secondly, he/she must be working under the influence of this mental illness during the commission of the crime.
  3. Thirdly, one committing the act must be incapable of knowing the nature of the act.
  4. Finally, the person must be incapable of distinguishing between right and wrong, at the time of the commission of the act.

Trial of John W. Hinckley Jr

One of the most infamous and earliest-known trials involving the insanity defense, where the defense was successfully upheld, was the trial of John W. Hinckley Jr[2]. In 1981, a man named John W. Hinckley Jr. attempted to assassinate President Ronald Reagan in Washington D.C. in a bid to impress actress Jodie Foster, with whom he was obsessed. He was held on charges of an attempted assassination but was acquitted by reason of insanity. The chief public reaction to this verdict was sheer outrage and it ultimately led to Congress passing the Insanity Defense Reform Act.

Case of Daniel Sickles

The first person to successfully use temporary insanity as a legal defense was Daniel Sickles, a U.S. Congressman. In 1859, Sickles was accused of murdering his wife’s paramour, Phillip Barton Key. Although he confessed to the murder, Sickles’ lawyer claimed that Sickles was “driven insane” by his wife’s infidelity. Hence, this was a case of temporary insanity. The jury took him for his word and Sickles was acquitted. [3]

It is evident that the defense of insanity has been around for a while and is constantly evolving, like most things in law. It has undergone various changes with respect to its exact definition and interpretation in law. And even after so many years, still remains to be a subject of controversy, and open to skepticism and doubt with regards to its credibility in a court of law. It is also very rarely used and has a poor success rate.

English law on the defense of insanity

Under English law, insanity is a valid defense of crime. The fundamental definitions and current wordings of the law come from the M’Naghten Rules, which are based on the trial of Daniel M’Naghten in 1843. Currently, there are two applications of the insanity defense –

  • Where it is claimed that the defendant was “insane” at the time of the commission of the crime.
  • And, Where it is claimed that the defendant was “insane” during the trial.

Thus, making one incapable of effectively defending himself.

The House of Lords asked the judges of common law courts to formulate some basic principles which will provide the basis for the law governing legal responsibility in cases of insanity in England. These principles are:

  1. All are presumed to be sane and have enough reason until proven otherwise, to be responsible for their crimes.
  2. It must be clearly demonstrated, in order to establish a defense of insanity, that at the time of the commission of the act, the defendant was working under a defect of reason or mental illness, such that,
  3. The defendant was unable to understand what he was doing, and
  4. The defendant was unable to understand that what he was doing was wrong.

Therefore, the accused must prove, beyond any reasonable doubt, that he was indeed suffering from a mental defect at the time of the commission of the act, as a result of which he was incapable of appreciating the nature and quality of the act and the fact that what he was doing was wrong.

Indian law on the defense of insanity

The defense of insanity is provided in accordance with Section 84 of the Indian Penal Code, 1860 under the Indian law. Section 84 of IPC is solely based on the M’Naghten Standard and no changes have been made in it ever since it was first drafted. The principles laid down under the M’Naghten Standard apply to the Indian law as well.

Section 84 of IPC states that “Act of a person of unsound mind – Nothing is an offense which is done by a person who, at the time of doing it, by reason of unsoundness of mind, is incapable of knowing the nature of the act, or that he is doing what is either wrong or contrary to law”.[4] In Section 84 of IPC, the term “unsoundness of mind” is used instead of “insanity” as this term has a wider scope in terms of providing meaning and interpretation.

Major and Minor criteria

Section 84 of IPC can be divided into two broad categories for better understanding –

  1. Major criteria (requirement of mental illness): meaning the person was suffering from a mental illness at the time of the commission of the act, and
  2. Minor criteria (requirement of loss of reasoning): which means the person was:- (a) incapable of knowing the nature of the act, (b) incapable of knowing that the act is wrong, and (c) incapable of knowing that the act is contrary to law. Both of these criteria constitute legal insanity.[5]

Section 84 of IPC also clearly embodies two fundamental maxims of criminal jurisprudence, which are – (a) “Actus non facit reum, nisi mens sit rea”, which means an act does not constitute guilt unless done with a guilty intention, and (b) “Furiosi nulla voluntas est”, which means that a mentally impaired does not have free will and hence cannot form the frame of mind necessary to commit a crime.[6]

Therefore, Section 84 of IPC does not fasten culpability on persons with mental illness as the insanity defense is based on the idea that the mental defects can interfere with an individual’s ability to form “mens rea” as required by law.

The burden of proof under Indian law

The onus of proving the defense of insanity and providing evidence to prove its existence of circumstances lies on the accused under Section 105 of the Indian Evidence Act. The accused has to prove this by providing material such as expert evidence, oral and other documentary evidence, presumptions, admissions, or even prosecution evidence in court, such that it underlines the fact that he was indeed “insane” at the time of the commission of the act and could not ascertain the nature of his act or the fact the act is wrong or contrary to law.

  • Anandrao Bhosale v. State of Maharashtra

In Anandrao Bhosale v. State of Maharashtra[7], the Supreme Court held that it is crucial to prove that the point of time at which the accused was working under this state of “unsoundness of mind” must be the same point in time when the crime was actually committed. The burden of proving this lies on the party which is claiming the benefit of Section 84 of IPC.

  • Dahyabhai Chhanganbhai Thakker v. State of Gujarat

In Dahyabhai Chhanganbhai Thakker v. State of Gujarat[8], the court held that even if the accused is unable to conclusively establish that he was insane during the act, the evidence that is placed before the court may raise questions with regards to the basic elements constituting an offense, including mens rea of the accused and in that case the court would be entitled to acquit the accused on the ground that the general burden of proof resting on the prosecution was not appropriately discharged.

  • T.N. Lakshmaiah v. State of Karnataka

In T.N. Lakshmaiah v. State of Karnataka[9], the court held that though the burden of proof rests on the accused, he/she need not prove the same beyond a reasonable doubt, and merely satisfying the preponderance of the probability that he was “insane” during the act would be enough.

  • Sudhakaran v. State of Kerala

In Sudhakaran v. State of Kerala[10], the court held that the burden of proof cast upon the accused is no higher than that which rests upon a party to civil proceedings.

Difference between Medical insanity and Legal insanity

To simply differentiate between the two, “medical insanity” refers to the condition of a person suffering from a mental illness, disorder or defect, and “legal insanity” refers to the mental state of a person during the commission of the crime. In legal insanity, the person also loses their reasoning power in addition to the mental illness, being under the influence of which, the crime is committed. Legal insanity is purely a legal concept as it is only concerned with the mental state of the person during the crime.

According to a medical perspective, it would be correct to say that any person, when committing a criminal act, is insane and therefore must be exempted from being held for the same. Although, according to a legal perspective, a person can be held for the crime as long as it can be established that he was able to distinguish between right and wrong and was aware that the act is contrary to law, during its commission.

  • Hari Singh Gond v. State of Madhya Pradesh

In the case of Hari Singh Gond v. State of Madhya Pradesh[11], the Supreme Court held that every mentally ill person is not ipso facto exempt from criminal responsibility. There is a distinction between legal insanity and medical insanity. And, the court is concerned only with legal insanity, not medical insanity.

  • Bapu @ Gajraj Singh v. State of Rajasthan

In the case of Bapu @ Gajraj Singh v. State of Rajasthan[12], the Supreme Court held that mere abnormality of mind, partial delusion, irresistible impulse, or compulsive behavior of a psychopath does not guarantee protection under Section 84 of IPC.

  • Surendra Mishra v. State of Jharkhand

In the case of Surendra Mishra v. State of Jharkhand[13], the Supreme Court held that Section 84 of IPC only caters to legal insanity and not medical insanity and therefore not every person suffering from a mental illness is exempted from criminal liability.

Thus, to avail for protection under Section 84, it is not enough to prove that the person is suffering from a mental illness. But, more importantly, evidence in support of the fact that the person could not differentiate between and right and wrong and reason that what he is doing is contrary to the law must be provided.

Loopholes in the defense of insanity

  1. The law itself is quite dubious and subject to skepticism because it is a very special case in which the accused confesses to having committed the crime but pleads to be exempted from not bearing the consequences for the same by reason of insanity. Such kind of claim is sure to be met with doubt by any normal, right-minded person.
  2. It is very easy to misuse the defense of insanity and escape from punishment. This is because it is difficult to prove whether a person was of sound or unsound mind during the commission of the crime. Hence, the decision solely rests upon the sagacity of the judge. Due to this, the law loses its purpose.
  3. While medical insanity can be proven fairly easily, proving legal insanity is an extremely arduous task as it is difficult to meet the essentials of Section 84 of IPC. Thus, it is possible that persons with a legitimate case of insanity may get convicted, and others who don’t may get acquitted.


Due to these loopholes, the defense of insanity has become a popular method for many criminals to escape from punishment. A highly skilled lawyer can sway the judge to give his client the benefit of the doubt. It all comes down only to that. In light of these facts, we can conclude that the law concerning the defense of insanity clearly needs to be analyzed thoroughly and amended. One such amendment can be to incorporate the law of diminished responsibility which involves partial defense to charges due to the “diminished” mental capacity of the accused during the commission of the act.

As we know, these days it is not that hard to come up with fake evidence. And as a result, justice cannot be served. This is evident especially when such a big loophole is present in the law for criminals to exploit. Thus, it is essential that the Hon’ble Supreme Court takes into account the shortcomings of the law in concern. It must provide a better alternative so that justice is upheld. For that, in the end, is the goal of any law.


arya nanal Arya Nanal | ILS Law College, Pune







[6] Supra note 5.









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