insanity defense(redirected from Mental disease or defect)
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Related to Mental disease or defect: Plea of temporary insanity
behavior directed to protection of the individual from injury.
character defense any character trait, e.g., a mannerism, attitude, or affectation, which serves as a defense mechanism.
insanity defense a legal concept that a person cannot be convicted of a crime if he lacked criminal responsibility by reason of insanity at the time of commission of the crime.
defense mechanism in psychology, an unconscious mental process or coping pattern that lessens the anxiety associated with a situation or internal conflict and protects the person from mental discomfort. In the theory of psychoanalysis, the ego, following the reality principle, conforms to the demands of the outside world, but the id (repressed unconscious), following the pleasure principle, pursues immediate gratification of desires and reduction of psychic tension. The superego (conscience or morality) may take either side. Defense mechanisms develop in order to control impulses or feelings that lead to inner conflicts, to reach compromises between conflicting impulses, and to reduce inner tensions. They help to manage or avoid anxiety, aggression, hostility, resentment, and frustration. Defense mechanisms are not pathological in themselves; they can be a means of dealing with unbearable situations. Among the most common defense mechanisms are denial, displacement, identification, projection, rationalization, reaction-formation, repression, and sublimation.
defense reaction a mental reaction that shuts out from consciousness ideas not acceptable to the ego. See also defense mechanism.
in forensic psychiatry, the use in the courtroom of insanity as a mitigating factor in the defense of an accused on trial for a serious criminal offense. See: criminal insanity.
insanity defenseForensic psychiatry A legal defense that a person cannot be convicted of a crime if he lacked criminal responsibility by reason of insanity–a term defined as a matter of law; the premise is that where there is no mens rea because of insanity, there is no criminal responsibility. See American Law Institute Formulation, Durham Rule, Irresistible impulse test, Long Island Rail Road massacre, M'Naughton Rule. Cf 'Black rage' defense, Television intoxication, 'Twinkie' defense.
In legal and forensic medicine, the premise that an insane person who commits a crime is not legally responsible for that act.