- 1. An outmoded term referring to severe mental illness or psychosis. 2. In law, that degree of mental illness which negates the individual's legal responsibility or capacity. [L. in- neg. + sanus, sound]- criminal i. in forensic psychiatry, a term that describes the degree of mental competence and that is defined by such currently applicable legal precedents as the American Law Institute rule, Durham rule, M'Naghten rule, and the New Hampshire rule.- i. defense in forensic psychiatry, the use in the courtroom of i. as a mitigating factor in the defense of an individual on trial for a serious criminal offense. See criminal i..
* * *1) a severely disordered state of the mind usu. occurring as a specific disorder (as paranoid schizophrenia)2) unsoundness of mind or lack of the ability to understand that prevents one from having the mental capacity required by law to enter into a particular relationship, status, or transaction or that releases one from criminal or civil responsibility
* * *n.a degree of mental illness such that the affected individual is not responsible for his actions or is not capable of entering into a legal contract. The term is a legal rather than a medical one.
* * *in·san·i·ty (in-sanґĭ-te) [L. insanitas, from in not + sanus sound] mental derangement or disorder, a legal rather than a medical term denoting a condition due to which a person lacks criminal responsibility for a crime and therefore cannot be convicted of it. insane adj
Medical dictionary. 2011.