The Indian Penal Code,1860 is a substantive law which describes various crimes and explains the punishments for it. For an act to be a crime it should be accompanied by sufficient mental intent or mens rea as explained in the principle “‘actus non facit reum nisi infers sit rea”. The IPC provides various exceptions for the accused from Section 76-106. Some of these defences are based on the absence of mental intent – for instance, Section 82 of the IPC provides defence for the crime committed by an infant since the infant lacks sufficient maturity of understanding and mens rea. Similarly, Section 84 of the IPC, provides exception to the crime done by an insane person.
Section 84, IPC states that, “Nothing is an offence 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.”
As the Section states for a person to claim this defence, (s)he should not be able to know the nature of the said act or is unable to comprehend that the act is illegal or unlawful in nature. It is important to understand the distinction between medical and legal insanity. Medical insanity does not necessarily mean that the person is unable to understand the nature of his action, while this is an important aspect of legal insanity. This distinction was further explained in the case Hari Singh Gond v. State of Madhya Pradesh. In this case, the court said that the term insanity is describes the different levels of mental disorders. So a person who has mental disorder need not be able to avail the exception provided in Section 84 necessarily and that a court should only consider the legal insanity of the accused and not the mental insanity.
In Mohammed Rafiq Shahabuddin Shaikh v. State of Maharashtra, the Bombay High Court found that even a reasonable doubt in the mind of the court about whether the accused had a sound mind while committing the said act, then the accused is entitled to the defence provided in Section 84.
The law presumes that a person is innocent unless proved otherwise by the prosecution, so the burden of proof is on the prosecution. It is on the accused the burden of proof to prove that he or she deserves to avail the defence provided in IPC, that is, the law presumes that a person is legally sane unless proved otherwise by the accused. This is conformed in the Section 105 of the Indian Evidence Act.
KINDS OF INSANE PERSON
Though the concept of insanity is an entirely legal one, and not a medical one, a psychiatrist is often called to certify either the absence or presence of psychiatric illness as well as whether the accused is fit for trial. The psychiatrist can also consider impatient admission for the accused. There are four kinds of persons who are considered to not be of sound mind :
- An idiot : An idiot is considered to be of arrested development mentally and is unable to count till 20 years.
- Lunatic : A lunatic is a person who is not sane in certain intervals, that he has intervals of reason , but is not sane always.
- By illness: A person who has an illness which affect his/her sound mind, that is due to the illness he has become non compos mentis.
- By intoxication : A person who is intoxicated is considered to not have a sound mind.
One of the most important cases regarding the defence of insanity is the McNaughten Case. In this case the accused, McNaughten killed the Secretary of the Prime Minister while he intended to kill the Prime Minister since he was “asked to do so”. McNaughten used the defence of insanity which the court found he was entitled to since he was delusional. Following the acquittal of McNaughten, the Parliament formed a set of rules for application of the defence of insanity, which came to be known as McNaughten Rules. The McNaughten Rules is very similar to the Section 84, though the Section avoid the term “quality”. The Emarciano Lemos v State established that the foundation of the Section is McNaughten Rules.
The concept of legal insanity has been further explored in many cases and some of them are :
Surendra Mishra vs. State of Jharkhand
In this case, the accused Surendra Mishra came with a pistol and fired at point blank range at the deceased suddenly without any provocation. The accused was prosecuted under the Section 302 of the IPC and Section 27 of the Arms Act. The accused used the defence of insanity, by providing evidence for the psychiatric treatment showing that he was not in a state to understand the nature of his act. For this, the Supreme Court found the accused entitled to the protection of Section 84, IPC. The Supreme Court decided that every person who is suffering from medical insanity is not entitled to the exception provided by Section 84 and it requires the accused to prove legal insanity and not medical insanity. The Court also said that though the burden of proof is on the accused it is not necessary for him/her to prove it beyond all reasonable doubts, rather the ‘preponderance of probabilities’.
Ashiruddin Ahmed v. State 
In this case the accused saw a dream in which he was ordered to kill his five-year old son. The accused thinking that it was the command of the God, took his son to the mosque and killed his son, following which he went to his uncle and narrated the event. The accused used the defence of insanity which was granted to him by the court.
Siddhapal Kamala Yadav v. State of Maharashtra
The accused murdered a person using a saline stand and when the police constable attempted to arrest him by placing handcuffs on him, he tried to escape. The accused in the court pleaded not guilty, claiming the defence of insanity. But the court found that the fact that the accused attempted to escape when he was handcuffed shows that he had a sane mind and was aware of the consequences of his actions, and hence rejected his defence and was found guilty of Section 302.
Thus, the concept of legal insanity requires the accused to not be aware of the nature of his actions. If it is proved by the accused that he was of unsound mind during the commission of the act, then it is said to be “non compos mentis”. This defence lays on the foundation that an act to be a crime should be coupled with a guilty mind.
 Hari Singh Gond v. State of Madhya Pradesh, AIR 2009 SC 31
 Mohammed Rafiq Shahabuddin Shaikh v. State of Maharashtra,2018 SCC OnLine Bom 1461
 Section 105, Indian Evidence Act,1872
 Surendra Mishra vs. State of Jharkhand, (2011) 11 SCC 495
 Ashiruddin Ahmed v. State ,AIR 1950 CrLJ 225.
 Siddhapal Kamala Yadav v. State of Maharashtra
Author: Crystal Ann,
2nd year, National University Advanced Legal Studies