Insanity defense

not guilty by reason of insanityinsanitycriminally insanetemporary insanityinsanity defenceinsaneinsanity plealegally insanereason of insanityguilty but mentally ill
The insanity defense, also known as the mental disorder defense, is an affirmative defense by excuse in a criminal case, arguing that the defendant is not responsible for his or her actions due to an episodic or persistent psychiatric disease at the time of the criminal act.wikipedia
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Forensic psychology

forensic psychologistforensicforensic psychologists
The defense is based on evaluations by forensic mental health professionals with the appropriate test according to the jurisdiction.
It involves understanding fundamental legal principles, particularly with regard to expert witness testimony and the specific content area of concern (e.g., competence to stand trial, child custody and visitation, or workplace discrimination), as well as relevant jurisdictional considerations (e.g., in the United States, the definition of insanity in criminal trials differs from state to state) in order to be able to interact appropriately with judges, attorneys, and other legal professionals.

Royal Commission on Capital Punishment report (1953)

1953 British Royal Commission on Capital Punishment reportRoyal Commission on Capital PunishmentThe commission's report
Legal definitions of insanity or mental disorder are varied, and include the M'Naghten Rule, the Durham rule, the 1953 British Royal Commission on Capital Punishment report, the ALI rule (American Legal Institute Model Penal Code rule), and other provisions, often relating to a lack of mens rea ("guilty mind").
The 1953 Royal Commission on Capital Punishment report was a recommendation responding to criticism of rules for the insanity defense in a criminal case.

Durham rule

product testDurham RulesDurham'' rule
Legal definitions of insanity or mental disorder are varied, and include the M'Naghten Rule, the Durham rule, the 1953 British Royal Commission on Capital Punishment report, the ALI rule (American Legal Institute Model Penal Code rule), and other provisions, often relating to a lack of mens rea ("guilty mind").
A Durham rule, product test, or product defect rule is a rule in a criminal case by which a jury may determine a defendant is not guilty by reason of insanity because a criminal act was the product of a mental disease.

Diminished responsibility

diminished capacitycapacity for rational thought had been diminishedDiminished capacity in United States law
Mitigating factors, including things not eligible for the insanity defense such as intoxication (or, more frequently, diminished capacity), may lead to reduced charges or reduced sentences.
This is an aspect of a more general insanity defense (see the M'Naghten rules).

People v. Serravo

It originated in the M'Naghten Rule, and has been reinterpreted and modernized through more recent cases, such as People v. Serravo.
People v. Serravo, Supreme Court of Colorado, 823 P2d 128 (1992), is a criminal case involving the meaning of "wrong" in the expression "incapable of distinguishing right from wrong", as it appears in the M'Naghten rule for the insanity defense.

Bigby v. Dretke

James Eugene Bigby
The United States Supreme Court (in Penry v. Lynaugh) and the United States Court of Appeals for the Fifth Circuit (in Bigby v. Dretke) have been clear in their decisions that jury instructions in death penalty cases that do not ask about mitigating factors regarding the defendant's mental health violate the defendant's Eighth Amendment rights, saying that the jury is to be instructed to consider mitigating factors when answering unrelated questions.
When the case came to trial in 1991, Bigby used the insanity defense with several psychiatrists testifying to his mental illness.

Excuse

exculpationExcuse (legal)justification
The insanity defense, also known as the mental disorder defense, is an affirmative defense by excuse in a criminal case, arguing that the defendant is not responsible for his or her actions due to an episodic or persistent psychiatric disease at the time of the criminal act.

ALI rule

ALI test
Legal definitions of insanity or mental disorder are varied, and include the M'Naghten Rule, the Durham rule, the 1953 British Royal Commission on Capital Punishment report, the ALI rule (American Legal Institute Model Penal Code rule), and other provisions, often relating to a lack of mens rea ("guilty mind").
The ALI rule, or American Law Institute Model Penal Code rule, is a recommended rule for instructing juries how to find a defendant in a criminal trial is not guilty by reason of insanity.

Foucha v. Louisiana

In Foucha v. Louisiana (1992) the Supreme Court of the United States ruled that a person could not be held "indefinitely".
Foucha v. Louisiana, 504 U.S. 71 (1992), was a U.S. Supreme Court case in which the court addressed the criteria for the continued commitment of an individual who had been found not guilty by reason of insanity.

Frendak v. United States

In the landmark case of Frendak v. United States in 1979, the court ruled that the insanity defense cannot be imposed upon an unwilling defendant if an intelligent defendant voluntarily wishes to forgo the defense.
Frendak v. United States, 408 A.2d 364 (D.C. 1979) is a landmark case in which District of Columbia Court of Appeals decided that a judge could not impose an insanity defense over the defendant's objections.

Crime of passion

crimes of passioncrime passionnelCrime passionel
This legal defense is commonly used to defend individuals that have committed crimes of passion.
In the United States, claims of "crimes of passion" have been traditionally associated with the defenses of temporary insanity or provocation.

Daniel Sickles

Daniel E. SicklesDaniel Edgar SicklesDan Sickles
The defense was first successfully used by U.S. Congressman Daniel Sickles of New York in 1859 after he had killed his wife's lover, Philip Barton Key.
He was acquitted after using temporary insanity as a legal defense for the first time in United States history.

Mens rea

intentmental statemental element
Legal definitions of insanity or mental disorder are varied, and include the M'Naghten Rule, the Durham rule, the 1953 British Royal Commission on Capital Punishment report, the ALI rule (American Legal Institute Model Penal Code rule), and other provisions, often relating to a lack of mens rea ("guilty mind").
It is this reasoning that justifies the defenses of infancy, and of lack of mental capacity under the M'Naghten Rules, an alternate common law rule (e.g., Durham rule), and one of various statutes defining mental illness as an excuse.

Archuleta v. Hedrick

In Archuleta v. Hedrick, 365 F.3d 644 (8th Cir.
Archuleta had been found not guilty by reason of insanity of assault and subsequently ordered to be confined in a prison mental hospital by the United States District Court for the Western District of Missouri after his successful insanity defense, as he was evaluated by a psychiatrist as dangerous.

M'Naghten rules

M'Naghten ruleinsanityM'Naghten standard
Legal definitions of insanity or mental disorder are varied, and include the M'Naghten Rule, the Durham rule, the 1953 British Royal Commission on Capital Punishment report, the ALI rule (American Legal Institute Model Penal Code rule), and other provisions, often relating to a lack of mens rea ("guilty mind"). The M'Naghten Rules of 1843 were not a codification or definition of insanity but rather the responses of a panel of judges to hypothetical questions posed by Parliament in the wake of Daniel M'Naghten's acquittal for the homicide of Edward Drummond, whom he mistook for British Prime Minister Robert Peel.
The M'Naghten rule (pronounced, and sometimes spelled, McNaughton) is any variant of the 1840s jury instruction in a criminal case when there is a defense of insanity:

Insanity

insanemadnessmad
However, in colonial America a delusional Dorothy Talbye was hanged in 1638 for murdering her daughter, as at the time Massachusetts's common law made no distinction between insanity (or mental illness) and criminal behavior.
In contemporary usage, the term insanity is an informal, un-scientific term denoting "mental instability"; thus, the term insanity defense is the legal definition of mental instability.

James Hadfield

Hadfield's Trial
The Criminal Lunatics Act 1800, passed with retrospective effect following the acquittal of James Hadfield, mandated detention at the regent's pleasure (indefinitely) even for those who, although insane at the time of the offence, were now sane.
James Hadfield or Hatfield (1771/1772 – 23 January 1841) attempted to assassinate George III of the United Kingdom in 1800 but was acquitted of attempted murder by reason of insanity.

Daniel M'Naghten

M'Naghten's case1843Daniel McNaughton
The M'Naghten Rules of 1843 were not a codification or definition of insanity but rather the responses of a panel of judges to hypothetical questions posed by Parliament in the wake of Daniel M'Naghten's acquittal for the homicide of Edward Drummond, whom he mistook for British Prime Minister Robert Peel.
Through his trial and its aftermath, he has given his name to the legal test of criminal insanity in England and other common law jurisdictions known as the M'Naghten rules.

Philip Barton Key II

Philip Barton KeyPhilip Barton Key (U.S. District Attorney)
The defense was first successfully used by U.S. Congressman Daniel Sickles of New York in 1859 after he had killed his wife's lover, Philip Barton Key.
Sickles defended himself by adopting a defense of temporary insanity, the first time the defense had been used in the United States.

Criminal Lunatics Act 1800

Act for the Safe Custody of Insane Persons charged with Offenceschronic mentally ill offendercriminal lunatic
The Criminal Lunatics Act 1800, passed with retrospective effect following the acquittal of James Hadfield, mandated detention at the regent's pleasure (indefinitely) even for those who, although insane at the time of the offence, were now sane.
Before 1800, if a defendant was acquitted on the grounds of insanity, he was simply allowed to go free because there was no law in place that allowed the government to detain him.

John Hinckley Jr.

John Hinckley, Jr.John HinckleyJohn W. Hinckley, Jr.
After the perpetrator of President Reagan's assassination attempt was found not guilty by reason of insanity, Congress passed the Insanity Defense Reform Act of 1984.
He was found not guilty by reason of insanity and remained under institutional psychiatric care until September 2016.

Irresistible impulse

irresistible impulse test
The test, also called the Product Test, is broader than either the M'Naghten test or the irresistible impulse test.
In criminal law, irresistible impulse is a defense by excuse, in this case some sort of insanity, in which the defendant argues that they should not be held criminally liable for their actions that broke the law, because they could not control those actions, even if they knew them to be wrong.

Attempted assassination of Ronald Reagan

assassination attemptattempted assassinationReagan assassination attempt
After the perpetrator of President Reagan's assassination attempt was found not guilty by reason of insanity, Congress passed the Insanity Defense Reform Act of 1984.
A federal judge subpoenaed Foster to testify at Hinckley's trial, and he was found not guilty by reason of insanity on charges of attempting to assassinate the president.

Clark v. Arizona

In 2006, the Supreme Court decided Clark v. Arizona upheld Arizona's limitations on the insanity defense.
Clark v. Arizona, 548 U.S. 735 (2006), is a United States Supreme Court case in which the Court upheld the constitutionality of the insanity defense used by Arizona.

Durham v. United States (1954)

Durham v. United States
The strict M'Naghten standard for the insanity defense was widely used until the 1950s and the case of Durham v. United States case.
1954), is a criminal case articulating what became known as the Durham rule for juries to find a defendant is not guilty by reason of insanity: "an accused is not criminally responsible if his unlawful act was the product of mental disease or mental defect."