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mental disorder of such severity as to render its victim incapable of managing his affairs or of conforming to social standards. Today, the term insanity is used chiefly in criminal law, to denote mental aberrations or defects that may relieve a person from the legal consequences of his or her acts. The case of Daniel McNaughtan, who was found not guilty by reason of insanity after making an assassination attempt on British prime minister Robert Peel (1834), gave rise to the modern insanity defense used in many Western nations today. In the United States, the 1954 case of Durham v. the United States led to the establishment of new rules for testing defendants. Today, psychologists may perform tests to determine whether or not the defendant is mentally stable. Such tests try to ascertain whether or not a defendant can distinguish right from wrong, and whether or not he acted on an "irresistible impulse." John Hinckley's assassination attempt on Ronald Reagan (1981) became another landmark in the history of the insanity defense. The court's initial verdict of "not guilty by reason of insanity" generated public outcry and renewed interest in the verdict of "guilty but mentally ill," which is permissible in some states. This verdict allows defendants deemed mentally ill to be hospitalized but requires them to carry out a reasonable prison sentence as well. In 1983, the Supreme Court ruled it permissable to keep a mentally ill defendant hospitalized for a term longer than the maximum sentence for the crime with which the defendant was charged. Many have contended that the insanity defense is nothing more than a legal loophole, allowing serious criminals to escape imprisonment. In fact, the plea is rarely employed in the United States, and it is estimated that less than 1% of defendants have used it successfully. Recent years have seen the restrictions surrounding insanity defense considerably narrowed, with the sole criteria for a successful plea being the determination of whether or not the defendant knew he was breaking the law.


See R. Simon and D. Aaronson, The Insanity Defense (1988); R. Porter, A Social History of Madness: The World Through the Eyes of the Insane (1989).


Any mental disorder.
In forensic psychiatry, a mental disorder which prevents one from managing one's affairs, impairs one's ability to distinguish right from wrong, or renders one harmful to oneself or others.
Term previously used to indicate mental disorder; no longer used in medical contexts.


1. relatively permanent disorder of the mind; state or condition of being insane
2. Law a defect of reason as a result of mental illness, such that a defendant does not know what he or she is doing or that it is wrong
References in periodicals archive ?
If we want tomorrow to be better than today, the fastest and most reliable option is to avoid Einstein's definition of insanity.
And if that Einstein quote still doesn't quite encourage you to embrace "newness," perhaps this one from him will - "The definition of insanity is doing the same thing over and over again and expecting different results.
Texas pilot Joe Stack, who set his house on fire and flew his airplane into an Internal Revenue Service office in Austin, Texas, on February 18, was motivated by frustration with tax-protest activities, according to his 3,000-word suicide note chronicling his troubles with the IRS over the past 15 years: "I saw it written once that the definition of insanity is repeating the same process over and over and expecting the outcome to suddenly be different.
The definition of insanity is repeating the same things and expecting a different result.
Mr Justice Coulson accepted that Mr Porter was deeply disturbed and "delusional" when he set the fire at his home in Landican Lane, Bebington on March 27, 2001 - but nevertheless ruled he did not come within the tight legal definition of insanity.
The definition of insanity, they say, is doing the same thing over and over, while anticipating a different result.
If the definition of insanity is repeatedly doing the same thing and expecting a different result, Israel's policy has to be deemed "crazy.
Past research has demonstrated that different professions working in the legal system cannot agree on the definition of insanity (Weinstein & Geiger, 2003).
Stubbornly sticking with a policy that has achieved nothing in nearly 50 years is a pretty good definition of insanity.
As we know, the true definition of insanity is continuing to do the same thing year after year and expecting different results.
He argued, however, that it did not matter whether the resulting insanity was temporary, intermittent, or permanent, as long as his long-term substance abuse produced a mental defect or disease that meets the definition of insanity in Virginia.
It's been said that the definition of insanity is doing the same thing again and again, while expecting different results.