Home BlogArticlesLegalIPC Insanity as a Defence to Criminal Liability (Tests of Insanity, IPC Provisions, Medical and Legal Insanity)

Insanity as a Defence to Criminal Liability (Tests of Insanity, IPC Provisions, Medical and Legal Insanity)

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Insanity as a defence IPC Kanooniyat

I. INTRODUCTION – General Principle

As a general rule, in order to hold a person criminally liable, a criminal intent is necessary and therefore capacity of forming a criminal intent is a very relevant consideration in determining the criminal liability of a person. Therefore, those who are under a natural disability of distinguishing between good and evil, such as, idiots and lunatics, are not punishable by any criminal prosecution whatsoever.


The tests that have developed overtime in regard to insanity are as follows :

1. Wild Beast Test : According to this test a person can claim exemption from liability if by reason of unsoundness of mind he was unable to distinguish between good and evil and also did not know what he did.


2. Insane Delusion Test : This test was evolved in Hadfield case. In this case the accused was held as not guilty on the ground of insane delusion. This test and has been used to acquit individuals whose criminal or wrongful actions were caused by their delusions. 

3. The Irresistible Impulse test : This test has been recognized in some English cases. This test is not whether individual is conscious of right or wrong, or whether he had the knowledge of the consequences of his act, but whether he can properly control his action. The law relating to irresistible impulse is as follows :

  • Existence of irresistible impulse is not to presumed from mere absence of motive of criminal act. 
  • The plea of irresistible impulse cannot by itself be a defence, but should be a good defence only where there is evidence of an antecedent unsoundness of mind.  
  • In India also the plea of irresistible impulse is not available to a person with no mental disorder or insanity or otherwise acts of anger, jealously or revenge will also be exempted. 

4. Durham rule : This test lays down that, only because the accused was suffering from mental disease or defect at the time he committed the act in issue would not suffice. There must also be a casual relationship between the mental abnormality and the criminal act.  If it was proved that the offender was suffering from mental abnormality, then the burden of proof will lie upon the prosecution to prove beyond reasonable doubt that the act was not the product of such abnormality. 

M’Naghten Rules

In this case law relating to criminal responsibility in case of lunacy had been laid down, which form the basis of modern law on insanity. The following principles were given :

  1. Every man is presumed to be sane until contrary is proved to the satisfaction of the court.
  2. To establish the defence on ground of insanity, it must be shown that at the time of committing the act, the accused was under a defect of reason that he did not know that what he was doing was wrong. 
  3. A medical man who never saw the prisoner prior to the trial cannot be asked to give his opinion on the state of the prisoner’s mind at the time of commission of the crime because this question involves the determination of the truth of the facts deposed and it is not a question upon mere matter of science. But where the facts are not disputed and the question is substantially one of science only, then it can be allowed in general form, but it cannot be insisted as a matter of right. 


The Indian law on insanity is based on the abovementioned point (1) & (2) of M’Naghten Rules. It is contained in S. 84 of IPC and lays down the test of responsibility in cases of alleged unsoundness of mind. 

Ingredients of Section 84 of IPC

1. The Act must be done by a person of unsound mind;

2. Such person must be incapable of knowing :

  • the nature of the act or
  • that the act was contrary to law or 
  • that the act was wrong.

3. Such incapacity must be by reasons of unsoundness of mind of the offender.

4. The incapacity must exist at the time of doing of the act constituting the offence. 

The law presumes every person to be sane unless the contrary is proved. 


The term unsoundness of mind has not been defined by the code but is considered by some as equivalent to insanity. Insanity includes lunacy, mental derangement, mental disorder and so on. There are various degrees of insanity, but for it be an excuse it must reach the degree which is prescribed in S. 84. Mere unsoundness of mind is not a defence, it must be such as 

  1. Which affects the judgement of a person or
  2. Renders the person incapable of knowing the nature of the act or
  3. That he is doing what is wrong or contrary to law.  


Insanity to be a defence must be such so as to disable an accused person from knowing the nature and consequences of his act at the time of commission of offence. A man is said to be ignorant of the nature of the act when he is ignorant of the properties and operation of the external agencies which he brings into play. 


Insanity must exist at the time of committing the act constituting the offence. In coming to the conclusion, the relevant circumstances, behaviour and state of mind of the accused before and after the commission of the offence, has to be taken into consideration. 


The burden of proof is on accused and he need not prove his unsoundness of mind beyond reasonable doubt. It is sufficient if he establishes his case from the circumstances which preceded, attended and followed his crime. 

Case Law :- Mittu Khodia v. State of Orissa

Held : Mere absence of proof of motive would not by itself show that a person was insane although it could be a factor to be taken into consideration. 


It was held in State of Maharashtra v. GM Shinde, that if plea of insanity is raised by the accused, it is the duty of the prosecution to subject the accused to medical examination immediately. In case of failure on the part of the prosecution it may entitle the accused to seek the benefit of doubt. 


The question of sanity is relevant at the time of commission of crime. Besides this, there are three periods at which the sanity is relevant :

  1. When he is put up for trial;
  2. At the time of his conviction and 
  3. After he has been sentenced. 

In State of Rajasthan v. Vidhya Devi,  even before the challan was filed the accused was admitted to hospital where he remained for 9 months. It was held that accused is entitled to the plea of insanity as the circumstances clearly show the same. 

Case Law :-Phulabai v. State of Maharashtra 

Facts : Accused jumped with her child into a well in an attempt to commit suicide resulting in latter’s death. He was suffering from incurable illness. 

Held : The plea of unsoundness of mind was accepted on the ground that mere absence of medical evidence did not justify exclusion of common sense. 

Sr. NoMedical InsanityLegal Insanity
1. It is solely dependent on medical grounds. It depends on the factors required to be proved in a court of law to enable the accused to be acquitted of the charge. 
2.It is not a cogent ground of defence from criminal liability. It furnishes a strong ground of defence from criminal liability.
3.To existence of medical insanity can be proved with the help of medical evidence. To establish legal insanity the necessary elements of S. 84 IPC must be proved.

Though, medically a person may be certified as sane or insane but legally he will be held insane only if he successfully proves the requirements of the law u/s 84 IPC. If he fails to prove the same, the law presumes him to be sane at the time of commission of the crime, even though medically he may be insane at that time. 

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