Defense of
Insanity/Mental
Abnormality
S. 84 Act of a person of unsound mind
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.
Mental abnormality is one of the general exception to
criminal liability under penal law of the country.
‘actus non facit reum nisi
mens sit rea’ An act itself is not a crime unless done with guilty intention. Which is
absent in case of
insanity/mental abnormality.
The foundation of the law of insanity was laid down in
M’Naghten case
Essentials of S. 84
Unsoundness of mind
Kinds of Insanity-
◦ Delusion/Hallucination- State of mind where a person may be perfectly fit in respect of everything but may be
under a delusion in respect
of one particular thing.
◦ Somnambulism- Unconscious state as walking in sleep.
◦ Irresistible Impulse, Mental agitation, Annoyance & Fury- Merely loss of
control and not unsoundness of mind.
Unsoundness of mind at the time of committing the offence-
State of MP v. Ahmadulla: SC held that the burden of proof to prove that at the time of doing the act, he was
suffering from unsoundness of mind is on the accused.
Sheralli Wali Mohammed v. State of Maharashtra – (accused killed his wife and daughter with a
chopper)
Presumption of Sanity – S 105 of the Indian Evidence Act. (On the accused)
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