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This article is written by Shruti Mishra, currently pursuing B.A. LL.B (Hons.) from IIMT & School of Law (Guru Gobind Singh Indraprastha University). This is an exhaustive article which talks about the applicability of M’Naghten Rules in various situations.


Any act to be considered as criminal requires two essentials i.e. Actus Reus (a criminal act) and Mens Rea (guilty mind) to decide the criminal liability of the accused. In law, there are a series of defences to behaviour that would otherwise be illegal, one of the best-known defences is the defence of insanity. One usually hears “not guilty because of insanity”, but what does that mean and how does one determine whether the individual is insane or not. There are a lot of different tests and doctrines that can be used but the most prominent of these is the M’Naghten Rules, which was named after a man from England named Daniel M’Naghten. When a person commits a crime and uses a plea of insanity as a defence, the liability to prove his state of mind at the time of the commission of the criminal act lies on the defendant. Such a plea is expressed in the English doctrine – M’Naghten rules where for the first time, the court allowed the plea of insanity as a defence in the 1840s. This rule came up as a result of the case of Daniel M’Naghten in which he was acquitted for the murder of Edmund Drummond who he mistakenly identified as the British Prime Minister. M’Naghten was also under the impression that he was being persecuted by the political party which also proved that he was delusional. 

For further clarification and future reference, the House of Lords set up a panel of judges to come up with hypothetical questions regarding the plea of insanity as a defence, the panel came up with the answers that became the principles of the M’Naghten rule. The M’Naghten rules became a standard test to determine the mental state of the defendant and his criminal liability in common law jurisdiction. Once the rules of the standard test are satisfied, the accused is considered either guilty but insane or not guilty because of insanity. Insanity as a defence is presently recognised by many nations like the United Kingdom, India, Australia, Canada, the United States(in some states) etc.

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What are M’Naghten rules

As mentioned above, the acquittal of a murder charge with the defence of insanity in 1843, Daniel M’Naghten was found not guilty which led to the formulation of this rule. The M’Naghten rule is the standard test of insanity as a defence in England and other nations which was established by the English House of Lords in the 19th century. The panel of judges stated-

“Jurors ought to be told in all cases that every man is to be presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crime until the contrary be proven to their satisfaction. To establish a defence on the ground of insanity, it must be proved that at the time of committing the act, the party accused was labouring under such a defect of reason from disease of the mind as not to know the nature and quality of the act he was doing or he did not know that what he was doing was wrong.” 

In M’Naghten’s case, the medical experts argued that Mr M’Naghten did not have the required Mens Rea for the murder of the Prime Minister and when he was committing the offence, he was intellectually unaware of his actions because he was delusional. The purpose of this rule is not to root out all mentally disabled individuals from criminal responsibility but to exempt those who are incapable of making a rational decision.

Historical perspective

In history, there were many justifications for the plea of insanity to not comply with criminal responsibility. Once the mental capacity of the defendant is proved as a defence, that individual does not have to bear any criminal responsibility. The humanitarian approach suggests that treatment of the mental illness would be in the public interest rather than punishing the insane person. In the old days, insanity was given some consideration and there was some leniency in the given punishment, there was no codified law back then, so the insane person’s family gave compensation to the victim’s family. During the Norman times, there was no defence of insanity available, so if the jury found the accused to be guilty, he/she would get convicted but in special situations, the defendant was allowed to ask for forgiveness directly from the King. 

The early cases of English courts based upon the principles and laws regarding insanity were mostly in the 18th and 19th century, the earliest one was R. v Arnold 1724 16. In this case, the jury held that the actions of the man should clearly state that the individual was a madman and should be exempted from any criminal liability because the punishment is intended to set an example and to stop people from committing crimes but punishment to a madman can not be set as an example for the society. The man should be no more than “an infant or wild beast or a brute”, this was a test called “wild beast test” upon which Mr Arnold was found guilty and he got convicted for life imprisonment. Next major case was Hadfield’s Trial 1800 27 which challenged the relationship between insanity and the intellectual awareness of right and wrong. The jury decided that the delusion of the insane person should be believable and true, then only the crime committed would be exempted. This was considered a landmark case because it excluded the two previous perceptions of the court. First, it disconnected the relation between the intellectual awareness of the good and evil and second, it rejected the idea of a person being completely destitute of his mental state before his acquittal. Each jurisdiction has different levels or standards of determining if the accused’s insanity can be considered as a defence or not.

Nature of the act

The nature of the act is the state where the accused has no idea about his physical act that he performed e.g. the defendant slices a man’s hand into half but he is under the impression that he is cutting a loaf of bread. There were certain questions which were raised by the jury about the possible consequences of such acts which were committed by an individual who is insane or delusional or has no idea or knowledge that he/she committed a wrong act. It was considered that if the individual is committing an act under partial delusion or insane in other aspects, it will require considering all the facts and determining if the accused’s delusion was real or not. This rule requires the court to take into account Hadfield’s trial as well as the court, shall believe the facts stated by the accused just as the accused believes it to be. If the delusions are found to be false or unbelievable which proves his Mens rea, then insanity can not be used as a defence and the accused will be held accountable for his criminal actions. In the case of R v. Bell 1984, the individual committed a crime and said that God told him to commit such a crime. It was established that the accused was cognizant of his actions and therefore, he was not given the defence of insanity.

Applicability of the M’Naghten rule

Applicability of M’Naghten rules in the United States

The rules are applied to determine if the defendant was aware of the crime at the time of the commission of the act through cognitive standards. The M’naghten rules were later preceded by appropriate standards of insanity as a defence. The medical opinion, as well as psychiatric opinion, were added with the legal standards. In the United States, some of the States apply these rules concerning the penal code whereas some States apply variations of Model penal code. 

Applicability of M’Naghten rules in the United Kingdom

The rules or principles formulated after the M’Naghten’s case were added by the English Courts, which are binding in criminal trials. The rules have been criticised and argued many times by the legal and medical experts because these rules play a very important role in distinguishing whether the defendant was insane or not at the time of committing the criminal act. The defendant’s basic weakness is considered as a valid defence against criminal prosecution according to the M’Naghten test of criminality. The court applies M’Naghten rules to determine whether the disease claimed by the defendant is a disease of the mind which comes within the scope of the rules or not, like in England if the accused knew that his actions were legally wrong or contrary to the law then that is enough to justify that his action does not come under the scope of M’Naghten rules.

In the case of R v. Windle 1952 2 QB 826, it was held that the opinion of the accused or his idea of what’s right and what’s wrong is considered irrelevant, it doesn’t matter if the act was justified or not. If the act is legally wrong and the accused is aware of it, this will exclude him from the parameters of M’Naghten rules. 

Landmark judgments of ‘Defect of reason’ from ‘Disease of the mind’

In the case of R v. Clarke 1972 1 All ER  219, the accused took the defence of insanity saying that she was depressed and absent-minded at the time of the commission of the crime.  The accused was convicted by the assistant recorder. Later when she appealed to the court, it was observed that the accused had a defect of reason caused by the disease and the accused had no knowledge of the nature and quality of the act that she committed. The court stated that she had no intention of committing theft, her power to reason was caused due to diabetic depression caused by a deficiency of sugar (defect of reason) which comes within the scope of M’Naghten rules.

In the case of R v. Bruton (1863), a boy was murdered and the accused himself confessed his crime with full knowledge of all the happenings. He also gave a reason that he did the act with morbid feelings. For this crime, the court held him accountable for his criminal liabilities which shows that the absent mind’s power to reason or any confusion for a moment will not be covered under the M’Naghten rules. The judgement was given to clarify that the ‘defect of reason’ should be caused by the disease which affected the person’s mind, then only it will come under the M’Naghten rules.

In the case of R v. Quick 1973 QB 910, a nurse was charged for assaulting a patient. The accused took the defence of insanity on the grounds of automatism and pleaded not guilty. The court convicted the accused and stated that the medical evidence does not prove insanity. This appeal raised questions regarding the phrase ‘defect of reason’ from “disease of the mind’ comes within the rules. 

According to the M’Naghten rules, every individual is assumed to be sane and reasonable to be held liable for their actions unless the contrary is proved by the accused to the jury. The defence of insanity is established if the defect of the reason was caused by the disease of the mind and the accused was unaware of the nature and quality of the act he/she was committing. The rules were considered by the jury in English cases, these rules were implemented and accepted by the jury while making their decisions on whether to give a penalty or not in the criminal justice administration of England. This made it clear that the test of insanity is also dependent upon the kind of act one commits.

Applicability of M’Naghten rules in India

In India, the defence of insanity is accepted in the Indian Penal Code under Section 84 which deals with the crime committed by a person of unsound mind. This Section has a provision which the accused can use to relieve themselves from criminal responsibility on the grounds of insanity. Section 84 states “Nothing in an offence which is done by a person who at the time of doing it, because of unsoundness of mind, is incapable of knowing the nature of the act, or that he is doing any act which is either wrong or contrary to law.” This Section has basic principles or rules of criminal jurisprudence i.e. “Actus Facit Reum Nisi Mens Sit Rea”, this legal maxim means that the act does not make anyone guilty unless the accused had a criminal intention or committed the act with a guilty mind. Therefore, if an offence is committed by an individual who is proved to be of an insane mind, then it is considered that the accused had no mindfulness or rational thinking or guilty intention to commit a criminal act. Hence, the accused is not held liable for any criminal liability.

This Section is similar to the M’Naghten rules. There is a very niche distinction between the two. According to the M’Naghten rules, “The person is presumed to be sane unless the contrary is proved and the act must be followed by the defect of reason caused by the “disease of the mind” and the person was unaware of the nature and quality of the crime”. In Section 84, the term “quality” is not given and the term “contrary to law” is not provided under the M’Naghten rules. Many courts in India have interpreted Section 84 of the India Penal Code to the principles given in M’Naghten’s case.

Landmark judgements

Case- Amrit Bhushan v. Union of India 1976

In this case, the Supreme Court found that the M’Naghten rules define and explain the word “insanity” of the accused whereas under Section 84, the word “unsound mind” has been described which is equivalent to insanity. This was a step taken by the makers of the Indian Penal Code to give a wider scope to the term “unstable mind” and also recognised the non-compos mends (not in one’s right mind), which can be used as a defence of insanity under the criminal law. To get the defence under provision given in Section 84, some essential elements shall be satisfied i.e.

  1. The mind of the accused should be incapable of being aware of the nature of the act.
  2. The act should be contrary to law.
  3. The act should be wrong.
  4. To establish insanity or unsound mind of the defendant, his cognitive abilities of the defendant must be that he does not know his actions or the consequences of such an act.

Case- Emerciano Lemos v. State, 1969  

In this case, the accused slit-opened the throat of a person while he was having hallucinations and his mind was unbalanced. The accused had the knowledge of the nature or quality of the act and he knew that he was committing a wrong act yet he did not stop. Hence, the accused could not take the defence of insanity under Section 84 of the Indian Penal Code. The test of responsibility was prescribed by the court which was to be applied when the accused takes the plea of unsound mind under Section 84 of the Indian Penal Code. This test was added to help determine the Criminality of the Act. Other than the test of responsibility, this case also established that the M’Naghten rules are the fundamental source of Section 84 of the Indian Penal Code as they both have almost similar provisions.

All these cases and similarities prove that Section 84 contains the same substance as the M’Naghten rules and all the tests which have been prescribed in the M’Naghten rules e.g. mental capacity of the accused, the test to distinguish good and evil, the right and wrong test etc. are widely accepted and applied under the Indian Penal Code, to decide the criminal responsibility of the accused.

42nd report of Law Commission of India

In this report, the law commission of India recommended some amendments in Section 84 of the Indian Penal Code, these recommendations were made after serious considerations of laws of other nations which were based on insanity. 

The law report raised a few questions:

  • Should there be any variation, expansion or modification in the existing laws related to the defence of insanity? 

The majority of the opinions were opposed to the idea of any modification, expansion or variation in the existing laws of insanity under Section 84 of the Indian Penal Code. Most of them said that the current provisions are sufficient and making any kind of variations would likely cause further practical issues and if the decisions would depend upon the medical opinion, it will be hard to avail the necessary quality of medical experts all over India, especially in every district. If there is any special case which doesn’t come under the scope of Section 84, it would be left upon the decision of the President and Governor to decide what necessary steps are to be taken in that scenario, as they have the power of commutation and remission.

  • Should there be a test for the accused’s mental incapacity to know that such an act is wrong and punishable?

The majority of opinions opposed any such test. Some suggested that the test should be there to determine the accused’s knowledge of what is wrong or knowledge of that is punishable by law.

  • Should the accused be given the defence of insanity if he is incapable of resisting from doing the wrong action because of his mental capacity even though he is aware that the act is wrong or punishable?

In some views, adding such provision of ‘irresistible impulse’ in Section 84 would result in making the trial more difficult and complicated for the judge. There were questions raised on the language used in Section 84 that instead of using “disease of the mind” which is mentioned in M’Naghten rules, the Section uses the term “unsoundness of mind” which not only covers mental disease but also any kind of mental incapacity e.g. insanity, idiocy, feeble mindedness etc. and even a temporary hallucination may be considered under the term ‘unsound mind’.

Presumption of sanity and burden of proof

The court presumes that every individual is sane unless that person is proven otherwise, and hence the burden of proof lies on the party who is taking the defence of insanity. The standard of proof is on the probability or the chances of the individual being more likely to be insane than sane. This can either work in favour of the individual or against him. If the defendant succeeds in proving that the person was insane while committing the crime, the party that relied upon it would succeed. Whenever the defendant takes the defence of insanity, the prosecution can add evidence of insanity to minimize criminal responsibility. 

In the case of R v. Clarke 1972, the defendant shoplifted without realising that she was shoplifting. The burden of proof was on the accused, the accused claimed that she was suffering from depression and that she had no intention of stealing anything. The evidence showed that her insanity was within the scope of the M’Naghten rules. The court stated that it is established that she had no mens rea while committing such an act, she had no knowledge of the act and her conviction was rejected. On the basis that, the general rules apply to those cases where the reason for insanity is caused by the disease of the mind.


When the plea of insanity succeeds as a defence and the individual is exempted from the criminal liability of the criminal act committed, the court on humanitarian grounds gives the sentence for the treatment of the insane person for the interest of the society and also, to avoid any further mishappenings. The sentence is given under Section 5 of the Criminal Procedure Insanity Act 1964, where the sentence is fixed by law depending upon the offence that has been committed. The court passes hospital order (Section 37 of the Mental Health Act, 1983) and also a restriction order, limiting certain rights of the defendant as per Section 41 of the Mental Health Act, 1987. The court may also give a supervision order or an absolute discharge depending upon the requirement.

Criticism of the M’Naghten rule

  • The rules have been challenging for a lot of reasons and one of them is that the legal definition is not sufficient or advanced enough, the medical side has found it to be misleading and obsolete e.g. the compulsory hospitalisation of the insane person that may be ordered, even if the defendant is not medically insane. According to the European Convention of Human Rights, “an individual should be ordered for hospitalisation or detained with proper medical expertise only”. This was later adopted in English law as well through the Human Rights Act, 1998
  • There are several illnesses which can be controlled by medicines but might show temporary insanity like diabetes or epilepsy, these diseases are not recognised by the law and they don’t fall under the scope of the defence of insanity.
  • These rules are criticised to be insufficient in determining whether the defendant is a threat to the public or not. Also, it’s hard to distinguish between temporary insanity and permanent insanity.
  • It was also debatable that the rules are too relaxed for the defendant with serious mental illness to get discharged from their criminal liability arising from their actions regardless of how much disorder is caused.


The M’Naghten Rules were a thorough principle for penal liability which have played a very important role in the recognition of insanity as a defence globally and the British criminal Jurisprudence was the first to recognise such principles or rules. These rules became the source of law which were the topic of all disputes. Several tests were curated by the English Courts which helped clarify the applicability and scope of these rules. The applicability of the M’Naghten Rules varied from nation to nation depending upon their approach towards their respective domestic laws. Some nations did not incorporate these rules entirely, they integrated it with some added provisions to have a wider scope of the term “insanity”. M’Naghten rules were a standard test for the accused who took the plea of insanity and these rules helped in determining whether the person’s defence is true and believable which would help the court to decide the criminal liability of the accused. These rules were criticised by the Royal Commission for having such narrow grounds for judging a case, as it only involved the intellectual or rational actions of a human being. The rules were also criticised for not including the emotional facts, even after various advances in fields like neuroscience, psychology, medical science etc. have taken place over the past few years, which help understand the emotions of a human being and their functioning better. 

Like many other nations, India also adopted the principles of M’Naghten Rules which became the base of Section 84 of Indian Penal Code, allowing the defence of insanity to be used in criminal trials. Looking at the recent developments in the contemporary world, the scope of Section 84 in Indian Penal Code needs to be widened which would include ‘medical insanity’ to be exempted from the criminal responsibility, the necessary psychiatric treatment to be given to the unsound mind, the speedy trial of the accused who is of unsound mind and also including psychology to prevent any injustice etc. The Law Commission of India has made various recommendations for the changes that need to take place under Section 84 of the Indian Penal Code, their view is that the test needs to be altered rather than making a life-size change in the main principles, which seems like a very practical approach and should be taken into consideration.


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