Defence of Unsoundness of Mind or Insanity | Section 84 IPC 1860 /22 BNS 2023

•The expression ‘unsoundness of mind’ is not defined in the code but it is similar to the term ‘insanity’ as referred to in R. v McNaughten’s case.

•But the makers of the code have preferred the expression ‘unsoundness of mind’ instead of the word ‘insanity’. Because ‘insanity’ has a very limited scope whereas ‘unsoundness of mind’ covers a much wider area.

•The defence of unsoundness of mind provided in the code or sanhita is incorporated under Section 84/22 of IPC 1860/ BNS 2023, it states that nothing is an offence which is done by a person who, at the time of doing it, by the 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. This defence is based on the principles of McNaughten’s case.

•The expression ‘Unsoundness of mind’ covers both medical insanity and legal insanity. To avail the benefit of this exception the accused has to prove both medical as well as legal insanity.

•Medical insanity can be proved by showing a medical certificate but to prove legal Insanity the accused must prove that at the time of commission of the crime with which he is charged, because of unsoundness of mind, he did not know the nature of his act or that he was doing what was either wrong or contrary to law.

•Medically a person may be certified sane or insane but legally he will be held insane only if he successfully proves the requirement of section 84/22. If he fails to do so, the law presumes him sane at the time of commission of the crime by him, even though medically he may have been insane at that time.

•Some important cases containing principles to prove unsoundness of mind:


A. [McNaughten’s Case (1843) 4 St Tr (NS) 847]  this case laid down the following principles:-

1. Every man is presumed to be sane and to possess sufficient degree of reason until contrary is proved to the satisfaction of the court.
2. To establish the defence of insanity it must be clearly proved that at the time of committing the act the accused was labouring in defect of reason.
3. If the accused was conscious that the act which ought not be done or it was contrary to law then he would be punishable.



B. [Hari Singh Gond v State of Madhya Pradesh, AIR 2009 SC 31]

1. Firstly, the accused will have to prove the medical unsoundness to the extent that the accused loses the control upon his body and is not capable of making right decisions. The same can be done by the production of medical certificate.
2. Apart from medical unsoundness the accused has to prove legal unsoundness as well. Legal unsoundness can be proved by proving that due to medical unsoundness existing at the time of commission of the offence the accused was incapable of knowing the nature of the act and the act he was doing was either wrong or contrary to law.


C. What if the accused knew the nature of act:

In Kanbi Kurji v State 1960 Cr LJ 1200 Gujarat the Court held that if the accused was suffering from unsoundness of mind at the time of committing the murders and even though he knew the nature of his acts but not that he was doing was either wrong or contrary to law. He will be entitled to the benefit of this exception.

In this case the accused believed himself to be pure blooded sooryavanshi Arjuna of the Mahabharata. He had cordial relation with his family members. One day he killed his wife and the eldest son without any provocation. He then went to the sarpanch of the village and addressing him as Bhishma Pitamaha he told him that he had killed Bhangdi (meaning is wife) and Karna (meaning his son). The Court held that he was suffering from unsoundness of mind at the time of committing the offence.

D. [Rattan Lal v. State of M.P(2002)], the Court held that the crucial point of time at which the unsound mind should be established is the time when the crime is actually committed and whether the accused was in such a state of mind as to be entitled to benefit from Section 84/22 can only be determined from the circumstances that preceded, attended and followed the crime.

E. [Prem Singh v State of NCT of Delhi AIR 2023 SC 193] in this case Court held that the burden to prove unsoundness of mind is on the accused.


•Other important leading cases:

1. R. v Arnold (1724) 16 St. Tr. 695 (Wild beast test case).
2. Hadfield’s case (Insane delusion test).