justice, right, legal

Legal Insanity and What’s the Difference Between Legal Insanity and Mental Insanity

By hearing the word insane, we thought of a mentally disturbed person who is innocent as a child and cannot think like a normal person. If we talk about insanity in legal language, then it may differ. Yes, insanity is used as a defence in criminal liability. We use a word for insanity that is ‘unsound mind’ in Section 84. The mentally ill person can’t be able to differentiate between what is right or wrong even do not know the nature of the crime. The person who has an unsound mind commits a crime, so that person has to prove their insanity at the time of committing a crime. The burden of proofs relies on the defendant. If the defendant justifies his crime by saying that the act was done under the influence of insanity and he has a mental illness or a mental disorder, then this is not taken as a defense. Because it is a legal concept, you cannot take advantage of a medical illness. The concepts of legal and medical are different. In court, the defendant has to prove legal insanity. So, we will see in the article about legal insanity and also know what’s the difference between legal insanity and medical insanity through judgements, Supreme Court and high court cases, and some research.


The insanity defence, legal insanity, medical insanity, IPC 84, criminal liability

Unsound of mind, Section 84, talks about the insanity of a person and also states that the person is not aware of the act that he has done and is incapable of understanding the crime that he has committed. This offence counts as a no offence, and it has the absence of ‘men’s rea’ (guilty mind). In everyday life, someone is declared guilty or innocent in court for a crime. In some crimes, it’s found that the person has no reason to commit a crime or lacks knowledge of what to do, so he takes the plea of ‘unsound mind’. In Indian penal code Section 84, it says that ‘if the person is doing wrong or contrary to law and incapable of knowing that nature at the time he committed the crime, by the unsoundness of mind, then it’s no offence. (1) The accused is entitled to take advantage of Section 84. Proving innocence in insanity is not that easy because mental illness isn’t considered legal insanity. Legal insanity differs from medical insanity, and to prove medical insanity is not enough to prove your innocency. Criminal Procedure of Law, 1973 (Crpc), Chapter 25, Sections 328–339, deals with the provision that deals with the arrest and trial of an accused person who has an unsound mind. (3) It’s a very interesting and debatable provision to prove the insanity.


The research sources are bare acts. IPC 1860, CrPC 1973, IPC book written by the authors K.D. Gaur, Rattanlal Dheeraj, Indian Criminal Law 1965 (defence of insanity), college library, some online sources like Livelaw, Manupatra, Legal Service India, case studies from US laws from Google Reading some journals, articles, and reports from A.I.R., SC.com, the Times Now newspaper, etc. To find out what exactly legal insanity is and what medical insanity means. case study to elaborate more about insanity, the rules, and what makes insanity into legal insanity.


If we know the concept of the insane, then it’s derived from the ethics of Christianity and Roman jurisprudence. The legal insanity, if we talk about the concept, came from a popular rule that we use in India to determine whether the act was done under the insanity or not, and that rule is known as the MC Naughten rules. This rule came into effect in 1843, when a man assassinated a secretary (Edward Drummond) of prime minister Sir Robert Peel of Britain, believing that he was hatching a plot by PM against him, and he mistook Edward for Robert Peel and murdered him because he was suffering from insane delusion. In that case, the court acquitted him by establishing McNaughten rules. The rule was named Naughten because the accused’s name was MC Daniel Naughten. After that, when the legal insanity case is reviewed or heard by the court, the basis of the case is the McNaughten rules. The Naughten Rules are a test in which we check whether the crime was done under the insanity of others or not. The test said two things:
* The accused did not know the act of nature when he committed it, or
* Not know the act that he done is wrong or contrary to the law. (2)
The MC Naughten rules are followed in India as well. Like the Naughten test, there are several legal tests used to prove the legal insanity. This test is used by different states, like the irresistible impulse test, the Durham test, and the model penal test for the defence.
THE IRRESISTIBLE IMPULSE TEST: If they confirm that they are suffering from a mental disease or. A defect that makes it impossible to antagonist the paroxysm to commit a crime. (3)
THE DURHAM TEST: The accused took the defence of insanity if his act was done against the law under the mental disease or any defect. This test was developed in response to the case of Durham v. United States. (4) THE MODEL PENAL TEST: – At the time of crime conduct, the conduct of his criminal act is appreciable, And it confirms that his actions are as per the law. (5) In Section 84 of the IPC, the word ‘unsoundness of mind’ is used instead of insanity. In India, we use more comprehensive and meaningful words; basically, the word ‘unsoundness of mind’ was stated by Huda. (6)


To take advantage of Section 84, the accused has to prove insanity or non-compos mentis (not of sound mind) by fulfilling the test mentioned in this section:
1. The accused must not know the nature of the act, which means the defendant must take a defence in two ways under this: automatism and mistake of fact due to an unsound mind. Automatism means the act that is done under the unconscious or unaware, like a person who has somnambulism problems and, in that time, kills another person, which means he is unconscious and does not know the nature of the act. Now the mistake of fact, we took the example of the McNaughten case, where he misunderstood the secretary as pm of Britain and murdered him. The mistake of fact is that he did not know the person who was also believed that PM was plotting something against him. So, the mistake of fact took as a defense also. 2. The accused knows the act he did but does not know the nature of whether what he is doing is wrong, right, or against the law. To understand this, let’s take the example of Shibo Koeri. Shibo killed his uncle by severing his head from his neck and serving to Kali, believing his uncle was free from sins. At that time, the accused was found insane for not knowing whether the act was wrong or contrary to the law. (7)

SUPREME COURT DECISION REGARDING DEFENSE IN SECTION 84 SURENDRA MISHRA V. STATE OF JHARKHAND, in this case, the person held for criminal liability has to prove legal insanity, not medical insanity. Even if the evidence says that the accused is a mental disturbance, in the absence of specific proof from the doctor or the nature of the mental disturbance, this would not prove the accused was mentally unfit or insane at the time of the incident. (8)

X v. STATE OF NCT OF DELHI, it was held that at the time of the offence, the accused was suffering from mental illnesses, had been mentally ill for a long time, and was not aware of the nature of the act he committed at that time. Therefore, the court acquitted the accused. (9)

ASHIRUDDIN V. THE KING, in this case, the accused, who was ordered by someone from heaven, took his 5-year-old son to the mosque and stabbed him in the neck. Later, he talked to his uncle and quietly told him what he had done. In this case, the court allowed the accused to take a defence under Section 84 of the IPC because the act done by the accused itself said that he was not aware whether the act was wrong or contrary to the law. (10)

BAPU GAJRAJ SINGH VS. STATE OF RAJASTHAN, in this case, The court observed that basic abnormalities of the mind, such as delusion disorder, irresistible impulses, or behaving like a psychopath, provide no immunity under Section 84 because, according to the Naughten rule, not every person who is mentally ill is subjected to criminal liability. (11)

S.K NAIR VS STATE OF PUNJAB, In this case, the accused tried to attack a person with a machete. The injured person held him and said that I would report the incident to the senior authorities. The accused replied to that by saying that only you can report the authority when you are alive, and after stating this statement, the accused killed him by ‘Khukuri’. The accused took the defence of paranoia, a person who behaved wildly in insanity for some time and then became normal. But here the court observed that the accused was not insane at the time of the crime when he committed it because he stated the statement of threatening the deceased to kill him, so he did not report to the authorities, which means he knows the nature of the crime and has motives and intentions, so he was convicted under Section 302 of the IPC. (12)

SHERALLI WALI MOHAMMED V. STATE OF MAHARASHTRA, in this case, This court rejected the plea of insane The fact was that the accused killed his wife and children with a chopper and did not escape from there after the act he committed. The door was open, but he was not able to escape, but that doesn’t mean he is insane or that he did not have the morals to commit a crime. so abnormality of mind or psychopath did not rely on defence under the section of 84 IPC. While the court rejected his plea of insanity and charged him under Section 302 of the IPC (punishment of murder), (13)

RATAN LAL V STATE OF MADHYA PRADESH, in this case, the court held the accused was a lunatic; he had the habit of setting fire to his clothes and house. The psychiatric report also said he was insane because he remained silent, mostly didn’t talk to people, and was depressed, so in this case, the person needs treatment. So, the court held the accused was not held here under Section 435 for mischief and alleged to take defence under Section 84 of the IPC. (14)

HARI SINGH GOND V STATE OF MADHYA PRADESH, In this case, there arose doubt about the fairness of the investigation, and the court said that the legal test should be done partially, and this is very responsible work towards the investigator. The accused does not take plea under this defence because there was nothing abnormal in his behaviour or some strange behaviour that does not count under this section. The accused did not take defence under Section 84. The concept of what is legal insanity and medical insanity came up in this case because medical insanity is not enough to prove the insanity under the section. (15)


Through the analysis of the case, the concept of medical insanity and legal insanity Now, what are medical insanity and legal insanity? What’s the difference between these? Let’s see:
Medical insanity means a person who is suffering from mental weakness; any kind of mental illness is known as medical insane’. Legal insanity means the insanity or mental illness must have occurred at the time of the crime when he committed it. Also, not knowing the nature of crime at that time or not knowing that it is contrary to the law, you take the defence of Section 84.

Mere abnormality of mind or compulsive behaviour, and we can say the psychopaths, does not contain the defence under Section 84. This clarity or elaborative factual evidence of medical or legal insanity came from the case (Tofan vs. State of MP 2022).

The court says that the proof of insanity by medical is not enough to defend in Section 84; legal insanity must be proved for reliance under Section 84 or immunity under this section. So, we can say that we must prove the insanity by medical and legal means. Then the accused will be immune under this section. (16)


So the role of a psychiatrist is to treat mental health. Aside from that, they must appear in court to resolve some disputes and be asked to certify the nature of the crime committed by a person of unsound mind or who claims to be insane. If the defendant pleads of insanity, then the psychiatrist has to confirm by his expertise that he was insane at the time of the crime he committed. assessing the defendant’s mental state and observing their behaviour and emotions during the trial in court. The psychiatrist should consider admitting the patient for a detailed analysis of the defendant. The psychiatrist’s job is to not mislead the court and help during the trial by giving an honest and factual and clarifying objective opinion. NIMHANS (National Institute of Mental Health and Neurosciences) worked for patients and evaluated the cases from time to time. It revises and performs from time, to time requirements for the betterment of legal
FORENSIC PSYCHIATRIST ROLE; The word forensic is derived from the Latin word forum. Then, after some time, it gradually changed into forensic from forum. The means of forensic in Latin is open or public court. Forensic psychiatry is a sub-branch of psychiatry. Basically, they will help in the context of issues at the interface of legal issues. They have to study the crime that was committed by the criminal after they analyse the case study and work on their treatment. The goals mainly follow the forensic psychiatrist: the criminals assuring to get treatment of mentally ill, in cases where offender mental stability is in doubt, then the evidence related to it submitted to court. To work efficiently for the advancement of the relation between law and psychiatry, they should work with non-clinical experts and do not delay the treatment of offenders with mental disorders.


Proving a crime always relies on prosecution, and that can never change. The accused must prove that he was incapable of knowing the nature of the act. Section 84 of the Indian Penal Code presumes the sense of contradiction that the accused was not insane when he committed an act. In civil proceedings, the burden of proof is more on the party than in criminal proceedings. Lastly, if the accused was not able to prove he was insane at the time of committing the crime, then the other evidence that was submitted during the trial was all unreasonable, and the court would acquit the accused.


Sections 328 to 329 of the Code of Criminal Procedure Law apply to the accused when he is of sound mind and unable to defend himself. The magistrate will evaluate the accused on the basis of the medical report. The magistrate has the power to adjourn the hearing or release the unsound person. If bail is refused, he will remain in safe custody. And if the accused recovers or the condition gets better, he will be summoned by the court. After summons, the court told the accused to explain the nature of the crime. Everything will be handled in a proper manner so that justice will be given to a mentally ill person or someone with an unsound mind.


The Indian court wanted to be progressive, so they amended by English law the concept of diminishing. The modification of psychiatrists was also part of the progress because society changes from time to time, so we should be attentive and flexible towards the law according to society. So, the doctrine of diminished responsibility was introduced by the Homicide Act of 1957 as a defence to murder. According to this culpable homicide, it is not murder if the person committed a crime under the unsound mind at the time, he committed the crime. (17)

I thought there was misuse of this section, but in today’s time, the scenario seems like there is a high possibility that the defence of insanity is misuse for escaping from a crime. This is a very strong weapon that is used by defence lawyers to prove not guilty to the accused illegally. The court has to ensure that a wise person does not escape by using loopholes of provision that are wrongly used in his favor. The court has to more partially and factually believe and be elaborative and wide regarding these cases so that the innocent person is not charged falsely under the provision.


There is ignorance of medical insanity, which means the provisions are not more clear about mental illness. The concept is more focused on legal insanity, but there is some confusion because there is no clear definition of medical insanity. To defend a person, we should focus more on legal insanity, and psychiatrics should also be more partial so they guide the court properly. Investigators should also not, like in the Ratan Lal case, mislead the case because the investigator is not investing properly. The diminished responsibility concept talks about the defence under culpable homicide; it should also be more relevant regarding Section 84.


  1. ‘UNSOUND MIND’ section 85 IPC, Criminal Procedure law 1973, ch.25, section 328-329 K.D GAUR 
  2. www.jstor.com
  3. www.indlaw.com
  4. www.manupatra.com
  5. www.indiankanoon.com

1. Bare act by Universal, pg.no 22

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4676201/#:~:text=Section%2084%20of%20IPC%20deals,wrong%20or%20contrary%20to%20law.%E2%80%9D
3. https://www.findlaw.com/criminal/criminal-procedure/the-irresistible-impulse-test.html#:~:text=The%20existence%20of,to%20the%20law.
4. https://blog.ipleaders.in/insanity-defence-indian-penal-code/#Durham_Rule
5. https://www.findlaw.com/criminal/criminal-procedure/the-model-penal-code-test-for-legal-insanity.html#:~:text=Appreciate%20the%20criminality,of%20the%20law
6. Huda, SS, Principles of law of crimes in British India, p.271.
7. Gaur K.D, section 84, pg.no 263 (Ingredients of section 84)
8. https://www.livelaw.in/pdf_upload/71-prakash-nayi-sen-v-state-of-goa-12-jan-2023-457055.pdf
9. https://indiankanoon.org/doc/54051662/#:~:text=This%20Court%20has%20in%20the%20judgment%20that%20follows%2C%20accepted%20the%20Appellant%27s%20plea%20of%20defence%20of%20insanity%20under%20Section%2084%20IPC%20and%20acquitted%20him%20of%20the%20offence%20with%20which%20he%20was%20charged.
10. https://indiankanoon.org/doc/1101879/#:~:text=Our%20own%20opinion,to%20be%20right.
11. https://indiankanoon.org/doc/673880/#:~:text=The%20standard%20to,of%20this%20section.
12. https://indiankanoon.org/doc/253719/#:~:text=unable%20to%20accept,in%20this%20appeal.
13. https://indiankanoon.org/doc/1283052/#:~:text=We%20think%20that,this%20point%20either.
14. https://indiankanoon.org/doc/1915243/#:~:text=The%20behavior%20of%20the%20appellant,bail%20bond%20shall%20stand%20cancelled.
15. https://indiankanoon.org/doc/1395565/#:~:text=The%20standard%20to,of%20this%20section.
16. https://www.livelaw.in/columns/section-84-of-the-indian-penal-code-insanity-mcnaughten-section-45-of-the-evidence-act-mental-insanity-legally-insane-209028
17. https://blog.ipleaders.in/insanity-defence-indian-penal-code/#:~:text=The%20Doctrine%20of%20Diminished%20Responsibility%20was%20introduced%20by%20the%20Homicide%20Act%20of%201957%2C%20as%20a%20defence%20to%20murder.%20If%20this%20defence%20is%20established%2C%20it%20will%20entitle%20the%20offender%20to%20be%20found%20guilty%20of%20manslaughter%20(culpable%20homicide)%20instead%20of%20murder.%C2%A0

Aarti Rai

Asian Law College (affiliated to CCSU)