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 their actions due to a psychiatric disease at the time of the criminal act. This is contrasted with an excuse of provocation, in which the defendant is responsible, but the responsibility is lessened due to a temporary mental state. It is also contrasted with the justification of self defense or with the mitigation of imperfect self-defense. The insanity defense is also contrasted with a finding that a defendant cannot stand trial in a criminal case because a mental disease prevents them from effectively assisting counsel, from a civil finding in trusts and estates where a will is nullified because it was made when a mental disorder prevented a testator from recognizing the natural objects of their bounty, and from involuntary civil commitment to a mental institution, when anyone is found to be gravely disabled or to be a danger to themself or to others.
The M'Naghten rule(s) (pronounced, and sometimes spelled, McNaughton) is a legal test defining the defence of insanity, first formulated by the House of Lords in 1843. It is the established standard in UK criminal law. Versions have been adopted in some US states, currently or formerly, and other jurisdictions, either as case law or by statute. Its original wording is a proposed jury instruction:
that every man is to be presumed to be sane, and ... that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong.
In American jurisprudence, an excuse is a defense to criminal charges that is a distinct from an exculpation. Justification and excuse are different defenses in a criminal case. Exculpation is a related concept which reduces or extinguishes a person's culpability, such as their liability to pay compensation to the victim of a tort in the civil law.
In criminal law, diminished responsibility is a potential defense by excuse by which defendants argue that although they broke the law, they should not be held fully criminally liable for doing so, as their mental functions were "diminished" or impaired.
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. It was added to the M'Naghten rule as a basis for acquittal in the mid 20th century.
Articles related to criminology and law enforcement.
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. Examples in which such rules were articulated in common law include State v. Pike (1869) and Durham v. United States (1954). In Pike, the court wrote, "An accused is not criminally responsible if his unlawful act was the product of mental disease or mental defect."
Daniel M'Naghten was a Scottish woodturner who assassinated English civil servant Edward Drummond while suffering from paranoid delusions. Following his trial and its aftermath, his name has been given to the legal test of criminal insanity in England and other common law jurisdictions known as the M'Naghten rules.
In criminal law, automatism is a rarely used criminal defence. It is one of the mental condition defences that relate to the mental state of the defendant. Automatism can be seen variously as lack of voluntariness, lack of culpability (unconsciousness) or excuse. Automatism means that the defendant was not aware of his or her actions when making the particular movements that constituted the illegal act.
Isaac Ray was an American psychiatrist, one of the founders of the discipline of forensic psychiatry. In 1838, he published A Treatise on the Medical Jurisprudence of Insanity, which served as an authoritative text for many years.
Settled insanity is defined as a permanent or "settled" condition caused by long-term substance abuse and differs from the temporary state of intoxication. In some United States jurisdictions "settled insanity" can be used as a basis for an insanity defense, even though voluntary intoxication cannot, if the "settled insanity" negates one of the required elements of the crime such as malice aforethought. However, U.S. federal and state courts have differed in their interpretations of when the use of "settled insanity" is acceptable as an insanity defense and also over what is included in the concept of "settled insanity".
In the field of criminal law, there are a variety of conditions that will tend to negate elements of a crime, known as defenses. The label may be apt in jurisdictions where the accused may be assigned some burden before a tribunal. However, in many jurisdictions, the entire burden to prove a crime is on the prosecution, which also must prove the absence of these defenses, where implicated. In other words, in many jurisdictions the absence of these so-called defenses is treated as an element of the crime. So-called defenses may provide partial or total refuge from punishment.
Insanity in English law is a defence to criminal charges based on the idea that the defendant was unable to understand what he was doing, or, that he was unable to understand that what he was doing was wrong.
R v Sullivan [1984] AC 156 is a British House of Lords case in criminal law, and a leading modern authority on the common law defence of insanity.
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.
People v Schmidt, 216 N.Y. 324 (1915), is a criminal case interpreting "wrong" in the M'Naghten rule for an insanity defense.
The Royal Commission on Capital Punishment 1949–1953 reviewed the application of death penalty in the United Kingdom, including the questions of what crimes should receive the death penalty and what method of execution should be employed. The commission was set up by the Attlee government in an attempt to defuse the long-term political debate over capital punishment. The Royal Warrant establishing the commission instructed their inquiry to assume the retention of the death penalty. In their report, the Commission described their own task as "trying to find some practical half-way house between the present scope of the death penalty and its abolition"
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. It broadened the M'Naghten rule of whether a defendant was so mentally ill that he is unable to "know" the nature and quality of his criminal act, or know its wrongfulness, to a question of whether he had "substantial capacity to appreciate the criminality of [his] conduct". It also added a volitional component as to whether defendant was lacking in "substantial capacity to conform his conduct to the law". It arose from the case of United States v. Brawner.
Smith v. State, Supreme Court of Alaska 614 P.2d 300 (1980), is a criminal case which distinguishes between the ALI test and the M'Naghten rule in an insanity defense.
Kahler v. Kansas, 589 U.S. ___ (2020), is a case of the United States Supreme Court in which the justices ruled that the Eighth and Fourteenth Amendments of the United States Constitution do not require that states adopt the insanity defense in criminal cases that are based on the defendant's ability to recognize right from wrong. It was argued on October 7, 2019 and decided on March 23, 2020.
