Insanity defense

From New World Encyclopedia

This article is about the legal defense of insanity. For the medical meaning, see Mental illness.

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.

When a person has violated the law, committing a crime, they face judgment usually in the form of a trial by jury. If their guilt in terms of their actions is well-established, there is still the question of whether they know that what they were doing was wrong. The insanity defense is an excuse, a reason why the person should not be held criminally liable for their actions, based on the argument that they did not understand that their acts were wrong. The legal determination of their inability to distinguish right from wrong has been the subject of much controversy, as not all cases are clear-cut with the party clearly mentally ill. Yet it is clear that in a society that values the rights of all its members, those who were unable to realize that their acts were wrong should not receive the same type of punishment as those who knew they were committing a crime. The former require help, assistance and education to allow them to live in society successfully, while the latter generally must pay a penalty as well as being rehabilitated.


In criminal law, insanity may serve as a defense by excuse 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. In civil law, insanity renders a person unfit for entering contracts or other legal obligations. Insanity suggests that a person did not fully appreciate the nature of right and wrong in their actions.[1]

In a criminal trial, the insanity defenses are possible defenses by excuse, via which defendants may argue that they should not be held criminally liable for breaking the law, as they were mentally ill at the time of their allegedly criminal actions. It is important to note that the legal definition of "insane" in this context is quite different from the psychiatric definitions of "mentally ill." Also, the definition of insanity varies from one jurisdiction to another.[2]

The insanity defense is still in use in the United States, while Australia and Canada have renamed it the mental disorder defense, and Commonwealth nations tend to shy away from it, partially due to the stigma of the word "insanity."

In England and Wales, for instance, the use of this defense is fairly rare. It is more common for someone with a mental illness to use the fact that they were mentally ill at the time of the offense as mitigation (which is distinct from a complete defense, which is what insanity is), or to use their mental state at the time of the trial to alter their sentence if found guilty (That is, once found guilty they receive an order committing them to a hospital rather than a prison sentence). When insanity is used, the person may still receive a hospital order.

The insanity defense is available in most jurisdictions that adhere to human rights and have a rule of law, though the extent to which it can or should be applied may differ widely between jurisdictions: for example, as in cases involving the battered-woman syndrome. Where the self-defense defense is not available, a defendant may be forced to choose between an insanity defense and provocation.[3]

Defendants may prefer to use the special defense of diminished responsibility because if successful, they will not be labeled as insane. For diminished responsibility, sentences can range from an absolute discharge to life imprisonment.

All jurisdictions require that criminal defendants must be competent to stand trial, meaning that defendants understand the nature of the proceedings against them and are able to assist counsel in their defense. A person who is found to be mentally incompetent to stand trial is usually hospitalized for treatment until such time that the person is competent to stand trial. Competency does not address the guilt or innocence of a party, and so competency to stand trial should not be confused with the insanity defense.[4]


The concept of defense by insanity has existed since ancient Greece and Rome. Written evidence which details court dismissals on the grounds of "madness" date from medieval England. The first complete transcript of trials involving madness dates to 1724. The fate of insane defendants was uncertain in the United Kingdom until the Criminal Lunatics Act 1800, following the acquittal of James Hadfield, provided for their indefinite detention. Madness to most courts at this point meant someone totally deprived of understanding and with the mentality of an infant.[5]

In 1843, an assassination attempt on Prime Minister Robert Peel by Daniel M'Naghten brought the idea of insanity back to the fore front in civil law. M'Naghten claimed that Peel was trying to kill him and so attempted to assassinate him as a pre-emptive attack. M'Naghten was declared psychotic by medical personnel, and he was acquitted by the court by reason of insanity. So strong was the public backlash at this result that Parliament hastily sought to craft a new rule on insanity in courts. The ruling, based on M’Naghten’s case, essentially stated the definition of the insanity defense. This became known as the M’Naghten Rules, which became the general guidelines for the cognitive aspect of the insanity defense.[6]

Through the first half of the twentieth century, the insanity defense was expanded again. Courts began to accept the theories of psychoanalysts, many of whom encouraged recognition of the irresistible impulse defense. Many states enacted a combination of the M'Naghten rule supplemented with an irresistible impulse defense, thereby covering both cognitive and volitional insanity.[7]

In 1954, the Durham Law was passed into the courts. The Durham rule excused a defendant "if his unlawful act was the product of mental disease or mental defect." The rule was lauded by the mental health community as progressive because it allowed psychologists and psychiatrists to contribute to the judicial understanding of insanity. But it was also criticized for placing too much trust in the opinions of mental health professionals. It was only accepted in New Hampshire, and either rejected or not thoroughly examined by other states.[8]

In 1964, the American Law Institute (ALI) began to reassess the insanity defense in the course of promoting a new Model Penal Code. What emerged from the Model Penal Code Commission was a compromise between the narrow M'Naghten test and the generous Durham rule. The ALI test provided that a person was not responsible for criminal conduct if, at the time of the act, the person lacked "substantial capacity" to appreciate the conduct or to conform the conduct to the rule of law. The ALI test provided for both cognitive and volitional insanity. The ALI version of the insanity defense was adopted by more than half the states and all but one federal circuit.[9]

Legal determinants of insanity

The M'Naghten Rules, inter alia, state that a person may be "insane" if at

the time of the committing of the act, the party accused was laboring under such a defect of reason, arising from a 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 what he was doing was wrong.

During the mid-twentieth century, the M'Naghten Rule was gradually superseded in most jurisdictions in the United States by other tests.[10] Ironically, following the attempted assassination of another prominent political figure (president Ronald Reagan) the M'Naghten rule underwent a major revival such that it is the rule in the majority of states.

The Durham Rule or "product test" was set forth by the United States Court of Appeals for the District of Columbia Circuit in 1954 and states that "an accused is not criminally responsible if his unlawful act was the product of mental disease or defect." After the 1970s, US jurisdictions have tended to not recognize this argument as it places emphasis on "mental disease or defect" and thus on testimony by psychiatrists and is argued to be somewhat ambiguous.

The Brawner Rule by the District of Columbia Appeals set aside the Durham ruling arguing the ruling’s requirement that a crime must be a “product of mental disease or defect” placed the question guilt on expert witnesses and diminished the jury’s role in determining guilt. Under this proposal, juries are allowed to decide the "insanity question" as they see fit. Basing its ruling on the American Law Institute’s (ALI) Model Penal code, the court ruled that for a defendant to not be criminally guilty for a crime the defendant, “(i) lacks substantial capacity to appreciate that his conduct is wrongful, or (ii) lacks substantial capacity to conform his conduct to the law.”

It is noteworthy that this case was (1) decided by the District of Columbia District Court of Appeals and not the United States Supreme Court, and thus did not provide a national precedent, and (2) not based on constitutional arguments and was thus superseded by Congress in 1984 with The Insanity Defense Reform Act of 1984.

The federal Insanity Defense Reform Act of 1984 provides:

It is an affirmative defense to a prosecution under any Federal statute that, at the time of the commission of the acts constituting the offense, the defendant, as a result of a severe mental disease or defect, was unable to appreciate the nature and quality of the wrongfulness of his acts. Mental disease or defect does not otherwise constitute a defense.

This act, a response to the Hinckley verdict, eliminated the Irresistible Impulse Test from the insanity defense under federal law. The act also provided that "the defendant has the burden of proving the defense of insanity by clear and convincing evidence." Previously under federal law, the government had the burden of proving sanity.[11]

The Insanity Defense Reform Act mirrors the M'Naghten rules except that it requires the defendant suffer from severe mental defect, and places the burden on the defendant to prove by clear and convincing evidence (higher than the preponderance of the evidence standard required of the defendant by most states following the M'Naghten rules).

The notion of temporary insanity argues that a defendant was insane, but is now sane. A defendant found to have been temporarily insane will often be released without any requirements of psychiatric treatment. This defense was first used by U.S. Congressman Daniel Sickles of New York in 1859 after he had killed his wife's lover, Philip Barton Key, but was most used during the 1940s and 1950s. Since then, it has not been as successful.

There is also an idea of an irresistible impulse, which argues that a person may have known an act was illegal; but, because of a mental impairment, they could not control their actions. In 1994, Lorena Bobbitt was found not guilty of the felony of "malicious wounding" (the equivalent of mayhem), when her defense argued that an irresistible impulse led her to cut off her husband's penis. In the late nineteenth century some states and federal courts in the United States, dissatisfied with the M'Naghten rule, adopted the irresistible impulse test. This test, which had first been used in Ohio in 1834, emphasized the inability to control one's actions. A person who committed a crime during an uncontrollable "fit of passion" was considered insane and not guilty under this test.

Psychiatric evaluations

Those found to have been not guilty by reason of insanity are generally then required to undergo psychiatric treatment; except in the case of temporary insanity. Defendants found not guilty by reason of insanity are generally placed in a mental institution. Unlike defendants who are found guilty of a crime, they are not institutionalized for a fixed period, but rather they are held within the institution until authorities determine that they are no longer a threat. Authorities making this decision tend to be cautious; as a result, defendants can often spend more time there than they would have in prison (had they been convicted). In Foucha v. Louisiana (1992) the Supreme Court of the United States ruled that a person could not be held "indefinitely." People can be cured of mental illness with the proper treatment.[12]


In practice, a finding of "not guilty by reason of insanity" almost always requires that the defendant have been in a state of active psychosis (at the time the law was broken) and usually such findings involve a diagnosis of schizophrenia or schizoaffective disorder, but may even involve Bipolar disorder, particularly where the Bipolar disorder is accompanied by psychotic features. The use of the insanity defense in cases of psychopathy (antisocial personality disorder) is generally available only if the defendant has a co-occurring DSM-IV Axis I diagnosis, and then it becomes a difficult task for the forensic psychiatrist to determine whether the criminal act was the result of antisocial personality disorder or the Axis I diagnosis.[13]

Incompetency and mental illness

An important distinction is the difference between competency and criminal responsibility. Competency deals with whether a defendant is able to adequately assist his attorney in preparing a defense, make knowing decisions concerning trial strategy and whether or not to plead guilty or accept a plea agreement. Criminal responsibility deals with whether a defendant can be held legally responsible for his criminal behavior. Thus, competency deals with the defendant's present condition, while criminal responsibility deals with the defendant's state of mind when he committed the crime.

In the United States, a trial in which the insanity defense is invoked typically involves the testimony of psychiatrists who will argue that the defendant is or is not insane. If there is agreement between the prosecution and defense that the defendant is insane then typically a jury trial is waived and a trial occurs in front of a judge in which evidence is presented and a judgment rendered. If there is disagreement between the prosecution and defense, each will typically present expert witnesses to a jury which will decide whose witnesses to believe.

The legal concept of insanity is different from the psychiatric concept of mental illness. Frequently, a person whose mental illness is not under dispute will be determined sane as the court will argue that despite a "mental illness" the defendant should still be held responsible; such a ruling is known as either a Guilty but Mentally Ill (GBMI) or a Guilty but Insane verdict. Michigan (1975) was the first state to create a GBMI verdict. Sometimes a person without mental illness can be found to be insane; for example, a person who is acting under the influence of a drug that was involuntarily administered (though voluntary intoxication has been rejected by most jurisdictions as a defense to crime).


There are many different interpretations of "insane" and many different notions of how to deal with insane individuals.

Some opponents of the insanity defense, such as Thomas Szasz, believe that psychiatry itself emerged as a way to justify mercy, of making persons "exceptional" and thus not deserving of the harsh punishment we would as a society wish to dole out to people who had extremely selfish or widely shared rationales for their actions. Since extreme selfishness ("self-absorption") or broadly shared resentments, such as envy of the rich or hatred of another ethnic group, are somewhat infectious behaviors, it has been claimed by those of the "anti-psychiatry" movement that schizophrenia and other "mental illness" were defined into existence to protect those whose motives and behaviors were not so infectious, and whose offenses were thus unlikely to be repeated by others.

The public tends to believe that the insanity defense is used more often than it actually is, possibly because insanity defense cases tend to be of a high-profile nature. The insanity plea is used in the U.S. Criminal Justice System in less than one percent of all criminal cases, and only one fourth of those defendants are found "not guilty by reason of insanity."[14]

Some U.S. courts have begun to ban the use of the insanity defense and a 1994 Supreme Court ruling upheld the right of Montana to do so. Idaho and Utah have also banned this defense. In 2006, the Supreme Court decided Clark v. Arizona, reaffirming the prerogative of the states to deviate from or even totally abolish the insanity defense.

Famous insanity defense cases

In 1981, John Hinckley, Jr. attempted to assassinate President Ronald Reagan. Hinckley was prosecuted and acquitted of all charges by reason of insanity, and a resulting public outcry prompted Congress to enact legislation on the issue. Most states joined Congress in reevaluating the insanity defense after Hinckley's acquittal. The legislatures of these states modified and limited the insanity defense in many and varied ways. Some states shifted the burden of proof, and some limited the applicability of the defense in the same manner as Congress did. A few states abolished the defense entirely.[15]

The Hinckley verdict accelerated the adoption of "guilty but mentally ill" verdicts by states. The "guilty but mentally ill" verdict allows mentally ill defendants to be found criminally liable and requires them to receive psychiatric treatment while incarcerated, or, alternatively, to be placed in a mental hospital and then, when they are well enough, to be moved to a prison to serve their sentences. Laws allowing pleas and verdicts of guilty but mentally ill were first adopted in Michigan in 1975, and concurrent with or subsequent to the Hinckley trial were adopted by 12 more states.[16]

Lee Boyd Malvo, along with John Allen Muhammad, was responsible for the murders of ten people in 2002. He was nicknamed “D.C. Sniper” because the killings took place near Washington D.C. When Malvo went on trial for the October shooting of Linda Franklin, one of the ten people murdered, he pled not guilty by reason of insanity. His lawyers tried to prove that Malvo had been corrupted by Muhammad and could not be held responsible for what happened. The jury did not accept this defense and found him guilty of the murder on December 18, 2003.[17]

Andrea Yates was successful in her use of the insanity plea. According to Richard Vatz in his article Murderous Mothers, Andrea Yates was put on trial for the drowning of her five children. Her legal defense attempted to prove that she was insane when she committed the murders. A jury decided that she was mentally stable and thus able to stand trial for the murders. She was convicted and sentenced to life in prison. However, that sentence was overturned when she won on appeal that there was error in her doctor's testimony. She won her second trial and was judged Not Guilty By Reason of Insanity and placed in a mental health facility.[18]


  1. Lisa Callahan, Margaret McGreevey, Joseph Morrissey, Henry Steadman. 1993. Before and After Hinckley: Evaluating Insanity Defense Reform. (The Guilford Press. ISBN 978-0898622805)
  2. Callahan et al.
  3. Callahan et al.
  4. Find Law, 2007. Insanity Defense, Criminal Law. Retrieved October 11, 2007.
  5. Gary Melton, et al. 1997. Psychological Evaluations for the Courts: A Handbook for Mental Health Professionals and Lawyers. (The Guilford Press. Retrieved September 19, 2007. ISBN 978-1572302365)
  6. Melton, et al.
  7. Jeffrey Lehman. 2004, West's Encyclopedia of American Law. (Thomson Gale. ISBN 978-0787663674) Retrieved September 19, 2007.
  8. Lehman
  9. Lehman
  10. John Martin, 1998. The Insanity Defense: A Closer Look, Washington Post. Retrieved October 11, 2007.
  11. Find Law, 2007. Insanity Defense, Criminal Law. Retrieved October 11, 2007.
  12. Melton, et al.
  13. Melton, et al.
  14. Martin
  15. Ellsworth Fersch, 2005, Thinking About the Insanity Defense: Answers to Frequently Asked Questions With Case Examples. (iUniverse. ISBN 978-0595344123) Retrieved October 11, 2007
  16. Find Law, 2007. Insanity Defense, Criminal Law.
  17. Fersch. FAQ
  18. Fersch. FAQ

ISBN links support NWE through referral fees

  • Ahn-Redding, Heather. 2006. The Insanity Defense, The World Over. Lexington Books. ISBN 978-0739115916.
  • Callahan, Lisa. McGreevey, Margaret. Morrissey, Joseph. Steadman, Henry. 1993. Before and After Hinckley: Evaluating Insanity Defense Reform. The Guilford Press. ISBN 978-0898622805.
  • Fersch, Ellsworth. 2005. Thinking About the Insanity Defense: Answers to Frequently Asked Questions With Case Examples. iUniverse. ISBN 978-0595344123.
  • Lehman, Jeffrey. 2004. West's Encyclopedia of American Law. Thomson Gale. ISBN 978-0787663674.
  • Melton, Gary. Petrila, John. Poythress, Norman. Slobogin, Christopher. 1997. Psychological Evaluations for the Courts: A Handbook for Mental Health Professionals and Lawyers. The Guilford Press. ISBN 978-1572302365.
  • Szasz, Thomas. 1984. The Myth of Mental Illness. Harper Paperbacks. ISBN 978-0060911515

External links

All links retrieved March 3, 2018.


New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

The history of this article since it was imported to New World Encyclopedia:

Note: Some restrictions may apply to use of individual images which are separately licensed.