Insane Law and Legal Definition
An insane person is a person who does not know what s/he is doing, is lacking in mind and reason. She could have suffered such a deprivation of reason that s/he is no longer capable of understanding and acting with discretion and judgment in the ordinary affairs of life.
The following is an example of a case law on insane:
A defendant may plead that he is not guilty of the offense charged because he was insane at the time that he is alleged to have committed the unlawful act. A person is insane, if at the time the overt act was committed he was suffering such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing, or if he did know it, that he did not know he was doing what was wrong. [People v. Field, 108 Cal. App. 2d 496 (Cal. Ct. App. 1951)].