Insanity, or madness, is a general term for a semi-permanent, severe mental disorder. The concept has been used in a number of ways historically. Today it is most commonly encountered as a generic informal term, or in the more narrow legal context of criminal insanity. In the medical profession, it is nowadays avoided in favor of specific diagnoses of mental illness.In criminal law, insanity may serve as a defense for a person's criminal acts. In most U.S. states, legal insanity is not sufficient to avoid a guilty verdict, rather to be not guilty by reason of insanity it must be demonstrated that the defendant could not tell the difference between right and wrong. The prosecuted could be charged as "not guilty for reasons of insanity
