Not everyone who commits a crime has a criminal mind, some of them suffer from mental illness. In Indian law, people who are suffering from mental illness or disability are known as people of unsound mind. And the people who are of unsound mind have certain laws or defenses in their favor. The mental health laws in India are based on British Laws as the whole judicial system of India is based on English common laws.

In the late 13 century  complete madness  was first established as a defense of criminal offense in England by common law court and by the 18th-century madness definition evolved and insanity defense was available to a person who was suffering from unsound of mind and unable to understand anything or what he is doing.

According to Section 84 of Indian Penal Code:

any act done by a person who is of unsound mind at the time of doing an act and the person is incapable of knowing the nature of the act and the person does not know that the act which he is doing is wrong or contrary to law.
Which means if a person in the time of committing a crime is of unsound mind or have lack of understanding about what he is doing then he is exempted from criminal liability. [1]

In one of the landmark cases, Surendra Mishra versus State of Jharkhand Supreme Court of India stated that:
If the accused wants to get relief from all the liability of his acts under section 84 of IPC he has to prove legal insanity, not medical insanity. And  The scope and ambit of section 84 of IPC came up for consideration before the Court in case of [2]

Hari Singh Gond Versus State of Madhya Pradesh, (2008) it has been held that:
Section 84 lays down legal test responsibility in cases of alleged unsoundness of mind. There is no definition of 'unsoundness of mind' in IPC .

Now, what is legal insanity, and how it is different from medical insanity?

Actus reus and mens rea are two important and basic elements of a criminal act and the absence of any one of them constitutes no criminal act. Legal Insanity is mental illness or mental instability with loss of reasoning power and without reasoning power, there is no possibility of mens rea. Medical Insanity simply means mental illness or mental instability. Unsound mind and mental illness are still undefined in IPC and not every person who is suffering from mental illness or unsound mind is exempted from criminal liability.

There are various tests to prove a person legally insane, three of which are the wild beast test, Insane Delusion, and test of capacity to distinguish right and wrong. All these tests are laid by the Mc Naughten rule. In the 19th century Mc Naughten killed Edward Drummond mistaking him for Prime Minister Sir Robert Peel due to his mental illness and after hearing several medical witnesses he testified that he is insane, he was acquitted by the house of lords and a special committee formulated few rules for insanity as a defense and it was called Mc Naughten rules. Even section 84 of IPC is wholly based and drafted on Mc Naughten rule and since then no changes have been made to it till now, despite the fact that in 1971 attempt was made by the law commission of India to revisit section 84 of IPC.

The burden of proving an offense is always on prosecution but the burden of proof is on the accused too if he wants to prove his insanity or elements of section 84. [3]

In the landmark case of State of M.P versus Ahmadull AIR 1961, Court held that  the burden of proof that the mental condition of accused was, at the crucial point of time, such as is described by section, lies on the accused who claims the benefit of this exception vide section 105 of Evidence Act [Illustration (a)]. The settled position of law is that every man is presumed to be sane and to possess a sufficient degree of reason to be responsible for his acts unless the contrary is proved  and [4]in the case of T N Lakshmaiah versus the State of Karnataka, Court held that:
under Evidence Act, the onus of proving any of the exceptions mentioned in chapter lies on the accused though the requisite standard of proof is not same as expected from the prosecution. It is sufficient if an accused is able to bring his case within the ambit of any of the general exceptions by the standard of preponderance of probabilities .

Under the law, it is believed that every person is sane and knows about his acts and knows about the consequences of his actions. It is also presumed that a person knows about laws, so the burden to prove the accused not guilty is on the accused or his family but according to the TN Lakshmaiah case the burden of proof is on the accused but he is not required to prove about his insanity beyond any reasonable doubt.

In India, 27.6% of prisoners are suffering from a mental disorder. The concept of Insanity is huge not only in crimes but also in contracts. Making a contract with an insane person is void in the eyes of law. Insanity law is one of the important defenses to prove one's innocence as mental health plays a vital role in one's life and criminal acts. Courts of India are working in insanity laws but still definition of insanity remains undefined.

Sources:

1. Suresh Bada Math, Channaveerachari Naveen Kumar, and Sydney Moirangthem, Insanity defense: Past, Present, and Future [11/11/2020 at 8:30 PM, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4676201/
2. Angad, Defense of Insanity [12/11/2020 at 4:00 PM], http://www.legalserviceindia.com/legal/article-3140-defense-of-insanity.html/
3. Legal thirst, Indian laws for people with mental illness [12/11/2020 at 7:00 PM], https://legalthirst.com/indian-laws-for-people-with-mental-illness/.

End-Notes:

1. Surendra Mishra v. State of Jharkhand. 2011, 11 SCC 495.
2. Hari Singh Gond v. State of Madhya Pradesh, (2008) 16 SCC 109 = AIR 2009 SC 31
3. State of M.P. v. Ahmadull,AIR 1961 SC 998
4. T.N. Lakshmaiah v. State of Karnataka, (2002) 1 SCC 219