Insanity Defense Essay

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Outbursts of violence cast doubt on the psychiatric competence to assess insanity and to balance the need to protect society with the need to offer a competent response to the mentally ill, who committed criminal offenses.

Criminal law assumes that individuals act with free will and that they should be held responsible for their actions. Michael Gazzaniga claims that even though human brains are determined by biological mechanisms, individuals are still able to exercise their “free won’t,” that is, to choose otherwise than to commit an action.

In the eye of the law, an individual is guilty of a crime if two conditions are met: the defendant engaged in a forbidden conduct (actus reus); the defendant committed the act with criminal intent (mens rea). An exception to criminal responsibility and culpability includes a class of persons who suffer from a severe illness or disability that impairs their cognition (the ability to perceive reality and to make sound judgments about it) and volition (the ability to control one’s own behavior).

The insanity defense concept depends on the assumption that a person who is insane cannot be considered responsible for their deeds, because only those actions that are knowingly and willingly committed should be considered as an expression of the individual’s ability to address their behavior in a socially acceptable and legal manner. The insanity defense claims that a mental disorder or defect caused the accused to commit the crime. Under any federal statute, the insanity defense is an affirmative defense to a prosecution 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 or the wrongfulness of his or her acts. Sanity is a legal and not a clinical concept, and it is related to a plea of not guilty by reason of insanity. Despite using the same terms, legal interpretations of them do not equate with clinical definitions of mental disorders. An additional burden of proving insanity is placed by current federal laws for clear and convincing evidence. Mental health professionals have the responsibility of providing sound evidence at a criminal trial and to help a judge or jury determine whether a defendant is criminally responsible for an alleged offense.

An adequate clinical-diagnostic classification is still a necessary condition, but not a sufficient one, for an accurate psychiatric-forensic assessment insofar as two other aspects should be evaluated: (1) to verify whether at the moment of the offending act there was a condition of mental disease or defect, of which it would be important to specify the nature and extension; and (2) to estimate whether there was an etiological nexus between the defect and the impairment in the ability to appreciate the wrongfulness of the act or in the ability to refrain from it.

There should be an integration of this information with the criminogenesis and criminodynamic of the offense, which may constitute the expression of a pathologically motivated act. Most states use two insanity defense standards: the McNaghten standard and the American Law Institute (ALI) test.

The McNaghten rule is narrow and harder to satisfy; it includes only the cognitive components. An exception of prohibiting the intention of killing a person exists. If a person kills someone because they reasonably believe that they are under a serious and imminent danger, the individual might not be held criminally responsible for causing someone’s death. Legally, the person might not be found guilty despite the intention to kill.

The McNaghten rule combines three elements:

  • The presumption that the defendant is sane and responsible for their criminal acts; if this is missing then
  • The defendant must have been suffering from a defect of reason or from disease

of the mind to be found not guilty and be exempt from liability; and

  • The defendant must not know the nature and quality of the act he or she was doing, or if knowing it, he or she did not know that it was wrong.

In assessing guilt, the law is concerned not only with the wrongfulness of the action committed, but also with the individual’s state of mind at the moment the act was committed. When defendants lack the understanding of the consequences of their actions, and an appreciation of the wrongfulness of them, then there is an option for the not guilty by reason of insanity (NGRI) plea.

The insanity defense addresses the moral question of criminal responsibility and blameworthiness, the psychiatric question of the medically appropriate nature of the mentally ill offender, and the social policy question of the adequate means of protecting society from potentially dangerous individuals.

However, it is a classic example of a “tensile strength” theory of the law, as Ernest Roberts defined it in 1983. Every legal principle can only hold a certain amount of emotional or political tension. When a principle is pushed beyond its tensile strength by expansionist litigators or creative legislation it will simply fall apart. The idea of a person committing a crime and being acquitted offends public and moral conscience, not least because of some public misconceptions: the perception of its overuse, especially in serious and heinous crimes; the idea that people found not guilty by reason of insanity (NGRI) are released quickly; and the claim that NGRI acquitters are particularly dangerous. The fact that NGRI defendants spend longer time in confinement and hospitalization and are assessed regularly for social dangerousness does little to assuage this concern.

Dissatisfaction over insanity defense verdicts also stem from the assumption that focusing on cognitive impairments as the sole ground for an insanity acquittal is limited from various perspectives: scientifically unwarranted, psychiatrically unjustified, and inconsistent with the general purposes of the criminal law. In 1955, in response to these concerns, the ALI developed the substantial capacity test and incorporated it into the Model Penal Code.

Under the ALI test, person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he/she lacks substantial capacity either to appreciate the criminality (wrongfulness) of their conduct or to conform their conduct to the requirements of the law.

The ALI test for mental illness is broad and adds the volitional component: a defendant found guilty would be found mentally ill instead of mentally insane.

In 1975, the Michigan legislature enacted the first guilty but mentally ill (GBMI) statute, which has since been followed by over 20 states. The definition and provision of GBMI vary across states, but there is some agreement in three main aspects: (1) corpus delicti of the crime has been met beyond a reasonable doubt, (2) the defendant was mentally ill at the time the crime occurred, and (3) the defendant is not found to be legally insane at the time the crime was committed. The verdict of GBMI is reached if the defendant satisfies the ALI’s standards of substantial capacity and wrongfulness.

The GBMI verdict’s original intent was twofold: first, to reduce the number of acquittals by reason of insanity; second, to guarantee treatment for those offenders who needed it. It also plays a double role: to protect the public, because the mentally ill defendants will not be released if they are deemed still dangerous; and to guarantee treatment to those ill defendants who are in need of it. Research findings agree that the goal of treating the offender has rarely been meet, not least because of the inadequacy of mental health resources and their scarcity.

Distinguishing NGRI and GBMI is still quite complex. The former is an affirmative defense of a crime: the person, found not guilty and not responsible, can be subject to civil proceedings for their confinements, but cannot be criminally incarcerated or punished. The latter is a verdict: the defendant had a mental disorder at the time of the crime, which, however, does not diminish their legal guilt or criminal culpability.

Mental health experts are not alone in recognizing that the distinction between illness that significantly impairs judgment (i.e., mental illness), and illness that impairs a defendant’s capacity to appreciate the wrongfulness of his conduct (i.e., insanity), is not only scientifically and clinically vague but also quite difficult to assess. This leaves room for unlimited discretion to determine whether an offense has been committed and under which mental, volitional, or emotional state. Some critics claim that the GBMI verdicts absolve judges or juries from making a decision through their deliberations and from influencing how society and the law should define responsibility clearly.

The reality of GBMI then becomes quite disconcerting: it is equivalent to that of a “guilty” verdict, insofar as defendants found by jurors to be only partially culpable endure a more severe sentence than the one they would have received had they been found fully culpable. Moreover, despite the GBMI verdict appearing as an alternative to an insanity defense, by just limiting its use it does not increase effective treatment options or enhance public safety. As John Melville and David Naimark argued in 2002, GBMI is a double injustice. Jurors may use GBMI as a shortcut around difficult conflicts in ethics presented in an insanity defense.

It follows that some critics see the GBMI verdicts as unconstitutional. Some others perceive them as a denial of the right to treatment, given that not all GBMI statutes expressly guarantee treatment, while others employ a mandatory, vague language (e.g. the defendant shall be treated). Another criticism lies in the difficulty of imagining the correctional system as ever being fully equipped to deliver meaningful treatment to GBMI defendants. Many do not undergo any treatment at all, and when the sentence is served, offenders will then be released even if they still suffer from a mental illness. It seems that GBMI statutes encourage unconstitutional compromised verdicts.


  1. Borum, Randy and Solomon M. Fulero. “Empirical Research on the Insanity Defense and Attempted Reforms: Evidence Toward Informed Policy.” Law and Human Behavior, v.23/3 (1999).
  2. Fentiman, Linda C. “Guilty But Mentally Ill: The Real Verdict Is Guilty.” Boston College Law Review, v.26/3 (1985).
  3. Gazzaniga, Michael. Who’s in Charge? Free Will and the Science of the Brain. New York: HarperCollins, 2011.
  4. Melville, John and David Naimark. “Punishing the Insane: The Verdict of Guilty but Mentally Ill.” Journal of American Academy, Psychiatry and Law, v.30 (2002).
  5. Noffsinger, Stephen and Phillip Resnick. “Insanity Defense Evaluations.” Directions in Psychiatry, v.19 (1999).
  6. Roberts, Ernest. Lectures on Environmental Law. Cambridge, MA: Harvard Law School, 1983.
  7. Simon, Robert and Liza Gold. Textbook of Forensic Psychiatry. Washington, DC: American Psychiatric Publishing, 2004.
  8. West, Sara and Stephen Noffsinger. “Is This Patient Not Guilty by Reason of Insanity? How to Assess a Defendant’s Mental State at the Time of the Offense.” Current Psychiatry, v.5/8 (2006).

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