In criminal trials, the insanity defenses are possible defenses by excuse, that is, an affirmative defense by which defendants argue that they should not be held criminally liable for breaking the law because they were legally insane at the time of the commission of the alleged crime. A defendant making the insanity argument might be said to be pleading "not guilty by reason of insanity" (NGRI), which, if successful, may result in the defendant being committed to a psychiatric facility for an indeterminate period.

A defendant attempting such a defense will often be required to undergo a mental examination beforehand. The legal definition of "insane" is, in this context, quite different from psychiatric definitions of "mentally ill".

Insanity is a legal concept, not a psychiatric concept of mental illness. Whether a person has a diagnosed mental disorder, brain damage or other condition affecting brain functioning is not sufficient reason, from the court's point of view, to relieve them from all responsibility for illegal acts they may commit. A person may have a mental disorder and be a competent person in many other ways, able to write checks, handle his personal affairs, hold a job and carry on a variety of behaviors despite the mental illness. Likewise, a person may commit a criminal act, independent of the fact that he has a mental disorder.

It would certainly unduly stigmatize a person with a diagnosed mental illness to say that because of the mental illness he is not responsible for his behavior. Therefore, persons whose mental disorder is not in dispute will be determined "sane" as the court will decide that despite a "mental illness" the defendant was responsible for the acts he committed and he will be treated in court as a normal defendant.

If the person has a mental illness or defect (such as brain damage) and it is determined that the mental illness or defect interfered with the person's ability to determine right from wrong, and in some states the ability to conform his/her behavior to the letter of the law and other associated criteria a jurisdiction may have, and if the person is willing to plead guilty or is proven guilty in a court of law, some jurisdiction have an option known as Not Guilty by Reason of Insanity [NGRI], or lacking criminal responsibility.

For the court to accept that the mental disorder was responsible for the criminal act it must be shown that the defendant committed the crime because of the mental disorder. For example, the mental disorder interfered with his ability to determine right from wrong at the time the offense was committed, or interfered with the capacity to restrain one's actions.

In the United States, a trial in which the insanity defense is invoked typically involves the testimony of psychiatrists or psychologists who will present opinions on the defendant's state of mind at the time of the offense. Neuropsychologists are especially qualified for conducting such evaluations. In addition to cases where the dimensions of brain damage or developmental delays are at play, for which neuropsychologists are uniquely suited, neuropsychological data can also prove fundamental in supporting cases where a psychiatric disorder is at play. In cases where a defendant is supposedly suffering from a psychiatric condition, such as schizophrenia or bipolar disorder or severe depression, not only psychiatric symptoms but also cognitive symptoms associated with such conditions can be measured by a neuropsychologist. These data can be used as collateral evidence that indeed a psychiatric disorder is present. In addition, a neuropsychologist is particularly well suited to assess whether a defendant is exaggerating or faking symptoms.

History of the Insanity Defense and Current Standards

Early Precursors (This section is adapted from Psychiatry.US, 2004, Forensic Psychiatry || Insanity, Criminal Responsibility & Diminished Capacity: Introduction & Historical Perspective as retrieved on May 11, 2010 from http://www.psychiatry.us/articledetail.php) - The concept of defense by insanity has existed since ancient times. In ancient Rome, Latin tribes held various religious beliefs that included considering the insane to be divinely blessed, and therefore beyond the reach of human jurisdiction. On the basis of this tradition, the concept of insanity as exculpatory entered the ancient Roman legal system.

As early as the 6th century BC the Hebrew Scriptures alluded to a distinction between crimes where fault could be imposed and those that occurred without fault.  "It is an ill thing to knock against the deaf-mute, an imbecile, or a minor: he that wounds them is culpable, but if they wound others they are not culpable…for with them only the act is of consequence, while the intention is of no consequence" (Mishna 8:4).

Aristotle (384-322 BCE) wrote: "A person is morally responsible if, with knowledge of the circumstances and in the absence of external compulsion, he deliberately chooses to commit a specific act". 

Jesus is quoted as "Forgive them, father, for they know not what they do".

In Islamic jurisprudence there is recognition of the concept of "majnoon" meaning an insane person in Arabic, who is not to be held responsible for his criminal actions.

By twelfth century, the pre-English law began to recognize the concept of "madness" as it related to criminal responsibility and the state lords would grant pardon to individuals who committed a crime and were deemed to be "mad".  

Early English law allowed acquittal only for those with severe cognitive disorders.  In 1265, the Arch Deacon of Barnstable, held that "An insane person is one who does not know what he is doing, is lacking in mind and reason and is not far removed from brutes".

Prior to 1500, insane persons were convicted, but then granted a king's pardon, upon request of the jury. 

The "Wild Beast" Standard - The "wild beast" standard was codified in 1724 in the first complete transcript of an insanity trial (Rex v. Arnold Trial, 1724). This is the earliest example of full proceedings of an insanity trial. Judge Tracy defined insanity as: "it must be a man totally deprived of his understanding and memory and doth not know what he is doing, no more than an infant, than a brute or a wild beast". This established the "Total Insanity" or "Wild Beast Test" standard, which prevailed in England for more than 75 years.

However, Rex v. Hadfield (1800) expanded the scope of insanity defense and criteria for exculpation under English law. James Hadfield, in a pre-meditated act, shot at King George III; he was charged with treason. He was found to be delusional at the time of his offense.  The defense attorney, Lord Erskine, in arguing for modification to the total insanity standard, said  "By insanity, I mean that state when the mind is under the influence of delusions, where the reasoning proceeds upon something which has no truth…but vainly built upon some morbid image formed in a distempered imagination. Delusion, therefore, where there is no frenzy or raving madness, is the true character of insanity".  The trial judge directed a verdict of insanity.

Following the acquittal of James Hadfield, the fate of insane defendants was codified in the United Kingdom with the Criminal Lunatics Act of 1800, which provided for their indefinite detention.

The insanity plea was codified in English law with the M'Naghten Rules of 1843.

The "M'Naghten Rules"  - In 1843, Daniel M'Naghten, a Scottish woodcutter who apparently believed that the prime minister was the architect of the myriad of personal and financial misfortunes that had befallen him, murdered the secretary to the prime minister, Edward Drummond, in a botched attempt to assassinate the prime minister himself, Sir Robert Peel. During his trial, nine witnesses testified to the fact that he was insane, and the jury acquitted him, finding him "not guilty by reason of insanity." The subsequent public outrage convinced the English House of Lords to establish standards for the defense of insanity, the result subsequently referred to as the M'Naghten Rules.

The House Of Lords, having deliberated, delivered the following exposition of the Rules:

"every man is presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crimes, until the contrary be proved to their satisfaction; and that to establish a defense on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was laboring 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" (Queen v. M'Naghten, 10 Cl. & Fin. 200, 203, 210, 8 Eng. Rep. 718, 1843).

Prior to the M'Naghten Test, the jury question about the right and wrong was put generally as to whether the defendant could give sensible answers to questions about the rightness or wrongfulness of various sorts of actions. This test clearly stated that the jury question be shifted to whether the defendant knew that the specific criminal act was wrong.

The M'Naughten rule was embraced with almost no modification by American courts and legislatures (see Davis v. United States, 160 US 469 - Supreme Court 1896 [PDF]) for more than 100 years, until the mid-20th century. In 1998, 25 states plus the District of Columbia still used versions of the M'Naughten rule to test for legal insanity.

The test to determine if a defendant can distinguish right from wrong is based on the idea that the defendant must know the difference in order to be convicted of a crime. Determining a defendant's ability to do so may seem straightforward enough, but dilemmas often arise in cases in which the M'Naghten standard is used. For instance, some issues focus on whether a defendant knew that his or her criminal acts were wrong or whether he or she knew that laws exist that prohibit these acts.

One of the major criticisms of the M'Naughten rule is its rigidity as the rule was met only if a "yes" answer could be provided to the question: "does the defendant know right from wrong?". In addition, in its focus on the cognitive ability to know right from wrong, it fails to take into consideration the issue of control and how to evaluate and assign responsibility for emotional factors and compulsion. Psychiatrists and psychologists agree that it is possible to understand that one's behaviors are wrong, but still not be able to control one's impulses to commit them. To address this, some states have modified the M'Naughten test with an "Irresistible Impulse" provision, which absolves a defendant who can distinguish right and wrong but is nonetheless unable to stop himself from committing an act he knows to be wrong. (This test is also known as the "policeman at the elbow" test: Would the defendant have committed the crime even if there were a policeman standing at his elbow?).

The "Durham Rule" - The Durham Rule, a version of which was originally adopted in New Hampshire in 1871, was embraced by the Circuit Court of Appeals for the District of Columbia in the 1954 case of Durham v. United States. The rule, sometimes referred to as the "Product Test," as stated in the court's decision by Judge David L. Bazelon, held that "an accused is not criminally responsible if his unlawful act was the product of mental disease or defect." (Durham v. United States, 214 F.2d 862) [PDF].

In Judge Bazelon's view, The Durham Rule was a way of simplifying the M'Naghten Rule and the Irresistible Impulse Test, by creating a simple and open-ended insanity test. He later wrote that he meant to "open up the courtroom to all the information and analysis available to the scientific community about the wellsprings of human behavior." Bazelon hoped that the new rule would allow experts to bring to the jury and the public new insights into "the physiological and cultural, as well as individual psychological, factors contributing to criminal behavior." Bazelon intended it to be not a precise test but rather a loose concept comparable to the legal definition of negligence. Thus, he compared the term "fault" in the negligence context to the term "responsibility" in the Durham context. The meaning of such terms, he argued, would have to be determined by a jury in light of the facts relevant to each case.

However, The Durham Rule proved difficult in its implementation as the Circuit Court had provided no real definitions of "product," "mental disease," or "defect." In addition, rather than leading to a meaningful understanding of the psychiatric issues at play in an insanity defense, in its applications the Durham Rule reduced to answering the question: "Is the defendant's conduct the product of mental disease or defect?", a question to which a "es/no" answer needed to be provided. Currently, only the state of New Hampshire still uses the Durham Rule as a way to define insanity.

The Brawner Rule - Because the Durham Rule proved very difficult to apply, the Circuit Court abandoned it in 1972 in the case of United States v. Brawner, 471 F.2d 969 (1972) [PDF].

The court replaced it with a standard developed by the American Law Institute (ALI).

In 1962, The Model Penal Code, published by the American Law Institute, provided a standard for legal insanity that was a compromise between the strict M'Naghten Rule, the lenient Durham ruling, and the irresistible impulse test. Under the MPC standard, also known as ALI Test, which represents the modern trend, "A person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks substantial capacity to appreciate the wrongfulness of his conduct or to conform his conduct to the requirements of the law" (Model Penal Code § 4.01[1] [PDF]). The test thus takes into account both the cognitive and volitional capacity of insanity.

The A.L.I. standard also excluded those defendants whose mental illness or defect only manifested itself in criminal or antisocial conduct, thus addressing the conundrum of the serial killer whose only symptom of mental illness is the killing of his victims.

The court in Brawner's case, in coming to its conclusion, emphasized that no particular formulation of words provides an easy solution to the difficult problems involved in assessing the sanity of a person accused of committing a criminal act. Instead, the court asserted that criminal responsibility in such trials is best assessed by a properly informed jury that is not overly dominated by expert testimony. To help juries make such assessments, the court required experts to explain the underlying reasons for their opinions rather than giving yes-or-no answers to simplistic questions.

It is noteworthy that this case was decided by the U.S. Court of Appeals for the District of Columbia circuit and not the United States Supreme Court, and is thus not a national precedent, and was not based on constitutional arguments and was thus superseded by Congress in 1984 with the Insanity Defense Reform Act of 1984.

The Insanity Defense Reform Act of 1984 (U.S.)

In 1981, John Hinckley Jr. shot then-U.S. President Ronald Reagan, a secret service agent, a Washington police officer, and Reagan's press secretary James Brady. Hinckley claimed that he was trying to impress the actress Jodie Foster, with whom he was infatuated. He later described the incident in a letter to The New York Times as "the greatest love offering in the history of the world. ... At one time Miss Foster was a star and I was the insignificant fan. Now everything is changed. I am Napoleon and she is Josephine. I am Romeo and she is Juliet."

A jury acquitted Hinckley of 13 assault, murder, and weapons counts, finding him not guilty by reason of insanity. There was an immediate public outcry against what many perceived to be a loophole in the justice system that allowed an obviously guilty man to escape punishment. There were widespread calls for the abolishment, or at least the substantial revision, of the insanity-plea laws.

After John Hinckley Jr.'s acquittal, members of Congress responded to the public outrage by introducing 26 separate pieces of legislation designed to abolish or modify the insanity defense. At the time of Hinckley's trial, all but one federal circuit had adopted the A.L.I. "substantial capacity" test, and all the new proposals were aimed at creating a stricter federal standard that would avoid acquittals like Hinckley's in the future.

The debates on this legislation reflected the public's indignation over the Hinckley decision. Sen. Strom Thurmond criticized the insanity defense for "exonerat[ing] a defendant who obviously planned and knew exactly what he was doing." Sen. Dan Quayle claimed that the insanity defense "pampered criminals," allowing them to kill "with impunity."

This hyperbolic testimony was countered by psychiatric and legal professionals who called for the modification, rather than the total abolition, of the insanity defense, and ultimately the resulting legislation—the Insanity Defense Reform Act of 1984—was somewhat of a compromise. The insanity defense was not abolished, but the A.L.I. test was discarded in favor of a stricter version that more closely resembled M'Naughten. To qualify, an insanity defendant must show the mental disease or defect is "severe." The "volitional" prong of the test, which excused a defendant who lacked the capacity to control his behavior, was eliminated. In effect, Congress returned to the 19th century "right/wrong" standard, echoing Queen Victoria's response to the M'Naughten acquittal.

Congress also adopted a number of provisions that toughened procedural barriers to a successful insanity defense. Before Hinckley, the burden of proof in federal cases was on the prosecution to prove beyond a reasonable doubt that a defendant was sane. The post-Hinckley reform legislation shifted the burden to the defendant to prove with clear and convincing evidence that he was legally insane at the time of the crime. The scope of expert psychiatric testimony was severely limited, and stricter procedures governing the hospitalization and release of insanity acquittees were adopted.

Current Standards - In the wake of the Hinckley verdict, following Congress' lead, more than 30 states made changes to their insanity-defense statutes. Over the 1980s and 1990s, many shifted the burden and standard of proof in ways to make it more difficult to sustain an insanity plea, moving away from the A.L.I. standard back towards the more restrictive M'Naughten test. In addition to raising more procedural hurdles for a successful insanity defense, many states enacted laws providing for more restrictive confinement options for those acquitted by reason of insanity. Three states -- Utah, Montana, and Idaho -- abolished the defense altogether. On the federal level, Congress abolished the volitional prong in the Insanity Defense Reform Act of 1984 (18 U.S.C.A. §§ 1 note, 17).

As of 1998, the states were roughly split between the two standards: 22 states used some form of the A.L.I. rule, while 26 used a version of M'Naughten, with or without an irresistible impulse component (For more information on State Insanity Defense Laws see PDF Table  [ATTACH])

In Massachusetts, the insanity defense is based on evaluations by forensic professionals that the defendant was either incapable of distinguishing between right and wrong at the time of the offense, or was unable to control his or her behavior at the time of the offense, thus adopting the ALI Test as implemented in the case of Commonwealth v. McHoul, 1967.

Further Issues

Many state courts during the '60s and '70s, in addition to the popularity of the more expansive test for legal insanity among state legislatures, issued rulings demonstrating a growing concern with protecting the civil rights of the mentally ill. Many courts struck down laws providing for the automatic and indefinite confinement of defendants who had been acquitted by reason of insanity. The courts said that due process and equal-protection concerns required that those found not guilty but confined due to mental illness had the right to periodic reassessment of their mental health status and dangerousness. If the evaluations did not find justification for continued confinement, the defendants would be released. By the early 1980s, all but 10 state legislatures had responded to these decisions and reformed their laws to provide for such review procedures.

In Ford v. Wainwright 477 U.S. 399 (1986), the US Supreme Court upheld the common law rule that the insane cannot be executed. It further stated that a person under the death penalty is entitled to a competency evaluation and to an evidentiary hearing in court on the question of his competency to be executed.[7] In Wainwright v. Greenfield, the Court ruled that it was fundamentally unfair for the prosecutor to comment during the court proceedings on the petitioner's silence invoked as a result of a Miranda warning. The prosecutor had argued that the respondent's silence after receiving Miranda warnings was evidence of his sanity.[8 

Guilty But Mentally Ill (GBMI)- Since the post-Hinckley reforms, the biggest development in insanity defense law is the introduction of the "guilty but mentally ill" (GBMI) verdict in many states. A sort of hybrid alternative to an acquittal by reason of insanity, a defendant who receives a GBMI verdict is still considered legally guilty of the crime in question, but since he is mentally ill, he is entitled to receive mental health treatment while institutionalized. If his symptoms remit, however, he is required to serve out the remainder of his sentence in a regular correctional facility, unlike a defendant who was acquitted by reason of insanity, who must be released if it is determined he is no longer dangerous to himself or others. In 2000, at least 20 states had instituted GBMI provisions.

Usage and success rate  -Media coverage in the United States tends to dictate how situations are perceived by the public. A case using the insanity defense usually receives a lot more media attention because it is considered unusual or dramatic. This increased coverage gives the impression that the defense is widely used but this is not the case. According to an eight-state study the insanity defense is used in less than 1% of all court cases and is only successful in 26% of cases. Of those cases that were successful, 90% of defendants had been previously diagnosed with mental illness. [Schmalleger, Frank (2001). Criminal Justice: A Brief Introduction. Prentice Hall. ISBN 0130887293] The early-2000s cases of Lee Boyd Malvo and Andrea Yates are examples of high-profile use of the insanity defense; both are characterized by their dramatic circumstances

Psychiatric treatment and Involuntary commitment

Often jurors fail to understand or are not explicitly told that those who have been found not guilty by reason of insanity are not usually released and returned to the community. Usually they are required to undergo psychiatric treatment, except in the case of temporary insanity (see below). 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 held in the institution until they are determined not to be a threat. Authorities making this decision tend to be cautious and as a result, defendants can often be incarcerated for longer than they would have been in prison, even though in Foucha v. Louisiana (1992) the Supreme Court of the United States ruled that a person could not be held "indefinitely".

So far, in the United States, those acquitted of a federal offense by reason of insanity have not been able to challenge their psychiatric confinement through a writ of habeas corpus or other remedies. In Archuleta v. Hedrick, 365 F.3d 644 (8th Cir. 2004), the U.S. Court of Appeals for the Eighth Circuit ruled that individuals found not guilty by reason of insanity who later want to challenge their confinement may not attack their initial successful insanity defense:

The appellate court affirmed the lower court’s judgment: "Having thus elected to make himself a member of that ‘exceptional class’ of persons who seek verdicts of not guilty by reason of insanity...he cannot now be heard to complain of the statutory consequences of his election." The court held that no direct attack upon the final judgment of acquittal by reason of insanity was possible. It also held that the collateral attack that he was not informed that a possible alternative to his commitment was to ask for a new trial was not a meaningful alternative ("Federal Insanity Acquittees - Person Found Not Guilty by Reason of Insanity May Not Attack His Successful Insanity Defense in Habeas Petition". Journal of the American Academy of Psychiatry and the Law).

Several cases have ruled that persons found not guilty by reason of insanity may not withdraw the defense in an habeas petition to pursue an alternative. However, other rulings have allowed it. In State v. Connelly, for example, the petitioner who had originally been found not guilty by reason of insanity and committed for ten years to the jurisdiction of a Psychiatric Security Review Board filed a pro se writ of habeas corpus and the court vacated his insanity acquittal. He was granted a new trial and found guilty of the original charges, receiving a prison sentence of 40 years.

In the landmark case of Frendak v. United States, 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 - DC: Court of Appeals 1979)

Aid in Sentencing, Diminished Capacity and Related Factors

Diminished Capacity - Diminished capacity or "diminished responsibility" can be employed as a mitigating factor and in the United States is applicable to more circumstances than the insanity defense. For example, some jurisdictions accept inebriation or other drug intoxication as mitigating factors while intoxication is not accepted as an insanity defense on its own. If diminished responsibility or capacity is presented convincingly, the charges may be reduced to a lesser offense or the sentence may be more lenient.

Mitigating factor - 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. This ruling suggests specific explanations to jury is necessary to weigh mitigating factors.

Temporary Insanity - 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).

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.

Parts of this review were retrieved on May 5, 2010 from http://en.wikipedia.org/wiki/Insanity_defense.