Insanity is defined under Indian law as being incapable of knowing the nature of one's acts or that they are wrong or illegal due to unsoundness of mind. It can also refer to a mental disease affecting personality and interaction. To be found legally insane, one must not have known the nature of their act or understood it was wrong/illegal due to their mental state. There are two types of insanity - legal insanity considers one's consciousness of their acts while medical insanity considers previous/present behavior and conduct. The M'Naughten rule established in a famous case provides that if one is under a delusion, they must be judged as if the delusional facts were real, and one is not responsible

1. Topic : Insanity

2. INSANITY
Insanity is define under section 84 of Indian Penal Code,
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.
In common words, it can be defined as a disease of the mind
which effects the personality, mental status, critical faculties,
emotional processes and interaction with social
environment.

3. INGREDIENT OF SECTION 84
1. The accused was incapable of knowing the nature of the act.
Automatism and mistake of
fact due to unsoundness of
mind as a defense .
2. The accused was precluded by reason of unsoundness of mind from
understanding that what he was doing was either wrong or contrary to law
Wherein a man by reason of delusion is
unable to appreciate the distinction
between right and wrong.

4. Legal insanity Medical insanity
Legal insanity means “the
accused’s consciousness in
relation to him”
Medical insanity means “the
accused’s consciousness of the
bearing of his act on those
affected by it”
legal insanity deals with the
wrong-doer must be under
unsoundness of mind at the time
of the incidence, and he does
not know its nature and affects.
Medical insanity deals with the
person’s previous and present
conduct and behaviour.
Every legal insanity is medical
insanity.
Every medical insanity is not
legal insanity.
There is two types of insanity

5. NON COMPUS MENTIS
Not of sound mind , memory or understanding . This is a
generic term and includes all species of madness, whether it
arise from.
 Idiocy
 Sickness
 Lunacy
 Intoxication

6. One person named McNaughton, under delusion of persecution shot dead
Mr. Drummond, the private secretary of Sir Robert Peel, Prime Minister of
England. In fact, he wanted to kill Sir Robert Peel but since he could not
identify him properly, he shot dead Mr. Drummond by mistake. He was
later arrested and sent to prison. Since he was insane and there was no
English law at that time to fix criminal responsibility of an insane, a
committee of 14 judges were constituted to frame law which resulted in
“McNaughton's Rule” or “Legal Test” according to English law which
states
M’Naughten ‘s case

7. Rule in M’Naughten ‘ case
If a man suffers under a partial delusion only and is sane in other
respects, he must be dealth with as if the facts with respect to which
delusion existed were real.
An accused is protected not only when, on account of insanity , he was
incapable of knowing the nature of the act , but also when he did not
know either that the act was wrong or that it was contrary to law,
although he might know he nature of act itself.

8. Surendra Mishra v. State of Jharkhand ,1986
Hari Singh Gond v. State of Madhya Pradesh 2009
State of Madhya Pradesh v. Ahmadulla 1961
Ram Lal v. State Of Rajasthan 1997
Related case laws: