Insanity Defense

Insanity Defense in the United States

Assertion that mental disease excuses a criminal act. The insanity defense is built on the concept of criminal intent or mens rea, the “guilty mind.” Persons who are mentally ill, under terms of this defense, cannot be held accountable for their behavior because they have no criminal intent. While this proposition may be generally reasonable, there is no real consensus on how mentally ill a person must be to be excused from criminal responsibility. This lack of consensus is reflected in the several different standards or criteria used in the fifty states.

A number of states use the old (mid-nineteenth century) English standard, the M’Naghten rule. This test is also referred to as the “right and wrong” standard. Under this standard, a person is legally mentally ill if he or she does not understand the nature of the criminal act or know the act to be wrong. Other states use a modified form of the M’Naghten standard, which integrates the notion of the irresistible impulse. That is, while the person may have known an action was wrong, the mental illness prevented the persons from controlling his or her conduct. Still other states use the American Law Institute standard. Under this test, a person is criminally responsible if the mental illness pfevenfs him or her from possessing “substantial’ capacity”’ to “appreciate the criminality” of an action or to control behavior to the “requirements of the law.” Separate from the insanity issue is the matter of competency to stand trial. Competence does not relate to guilt, but rather to the capacity of a defendant to consult with counsel effectively and understand the meaning of the proceedings in which he or she is involved. When the competence of an individual is in doubt, a formal hearing is held to determine competency to stand trial.

See Also


Analysis and Relevance

The insanity defense is an affirmative defense in that it introduces a new fact issue to a criminal proceeding. The defense not only requires the state to prove guilt, if a not guilty plea is entered, but also offers evidence as to mental illness that eliminates culpability even if the criminal act can be proven. Like other affirmative defenses, the burden of proof in an insanity defense resides with the defendant. The defense has always been somewhat controversial, but the controversy heated substantially with the acquittal of John Hinckley on charges stemming from the attempt on President Ronald Reagan’s life. The insanity defense, however, is not frequently asserted. Many states have established an option for juries in insanity defense cases to find a defendant guilty but mentally ill. This verdict requires that the person be placed in a mental health facility to undergo treatment. The person remains institutionalized until recovery is deemed sufficient to transfer the person to some kind of correctional facility.

Notes and References

  1. Definition of Insanity Defense from the American Law Dictionary, 1991, California

Insanity Defense in the U.S. Legal History


The legal principle that a criminal act should only be punished if the offender was fully capable of distinguishing right from wrong.


See Also

  • Legal Topics.
  • M’naghten Rule.

    Further Reading (Articles)

    After Fears ruling, three other insanity defenses sought., Tulsa World (Tulsa, OK); August 11, 2006

    INSANITY DEFENSE IS RARE AND RISKY NOW.(Local/State), The Capital Times; January 5, 1998; Miller, Mike

    Insanity Defense, Gale Encyclopedia of Everyday Law; January 1, 2006

    Gender Matters in the Insanity Defense, Law and Psychology Review; January 1, 2007; Breheney, Christian Groscup, Jennifer Galietta, Michele

    Penalties stiffen for homicidal mothers; Jurors are not buying insanity defenses anymore, Telegraph – Herald (Dubuque); May 24, 2003; ASSOCIATED PRESS

    Insanity Defense: Not a Right; In Montana Case, Justices Give States Option to Prohibit Claim, The Washington Post; March 29, 1994; Joan Biskupic

    Insanity Defenses, The Washington Post; March 20, 2001

    A Failure to Pursue an Insanity Defense on Behalf of an Individual with a Mental Illness Does Not Necessarily Constitute Ineffective Assistance of Counsel, Developments in Mental Health Law; January 1, 2009; Hafemeister, Thomas L.

    James Holmes Insanity Defense: Judge Sees ‘Good Cause’ to Allow Plea Change, The Christian Science Monitor; May 13, 2013; Brown, Ryan Lenora

    Insanity defenses can erode the law, Chicago Sun-Times; February 8, 1992; Charles Krauthammer

    Insanity defense not an option ; Due to Idaho law, mentally ill teen could go to prison rather than hospital, The Spokesman-Review (Spokane, WA); February 3, 2002; Angie Gaddy Staff writer

    A Tall Order for Insanity Defense Experts Make Case for Revamping System, Daily Herald (Arlington Heights, IL); May 14, 2006; Gordon, Tony

    Is Insanity Defense a Constitutional Right?, The Washington Post; July 23, 2012; Barnes, Robert;

    The craziest reform of them all: a critical analysis of the constitutional implications of “abolishing” the insanity defense., Cornell Law Review; September 1, 2002; Nusbaum, Daniel J.

    Insanity Defense, Likely in Whitten Murder Trial, Not an Easy Tack, Daily Herald (Arlington Heights, IL); April 24, 2006; Kunz, Tona Kovac, Adam

    Insanity Defense Asks Jurors to Judge Person Rather Than Facts, The Washington Post; December 11, 2003; Henri E. Cauvin

    Virginia Court of Appeals (1) Limits Application of “Settled Insanity” Defense to Instances Where Substance Abuse Leads to a Permanent or “Fixed” State of Insanity, (2) Places Burden of Proof for Establishing Involuntary Intoxication on the Defendant, Developments in Mental Health Law; January 1, 2008; Hafemeister, Thomas L.

    Insanity defense: Rarely used and rarely victorious, The Boston Globe (Boston, MA); February 29, 1996; Brian MacQuarrie, Globe Staff

    Interview: Gerald Treece discusses the difficulties in using the insanity defense in Texas, NPR All Things Considered; March 13, 2002; ROBERT SIEGEL, SUSAN STAMBERG

    Insanity defense has varied over centuries, Bangor Daily News (Bangor, ME); March 20, 2010; JUDY HARRISON

    Insanity Defense: Open and Free Legal Research of US Law

    Federal Primary Materials

    The U.S. federal government system consists of executive, legislative, and judicial branches, each of which creates information that can be the subject of legal research about Insanity Defense. This part provides references, in relation to Insanity Defense, to the legislative process, the federal judiciary, and the primary sources of federal law (cases, statutes, and regulations).

    Federal primary materials about Insanity Defense by content types:

    Laws and Regulations

    US Constitution
    Federal Statutory Codes and Legislation

    Federal Case Law and Court Materials

    U.S. Courts of Appeals
    United States courts of appeals, inclouding bankruptcy courts and bankcruptcy appellate panels:

    Federal Administrative Materials and Resources

    Presidential Materials

    Materials that emanate from the President’s lawmaking function include executive orders for officers in departments and agencies and proclamations for announcing ceremonial or commemorative policies. Presidential materials available include:

    Executive Materials

    Federal Legislative History Materials

    Legislative history traces the legislative process of a particular bill (about Insanity Defense and other subjects) for the main purpose of determining the legislators’ intent behind the enactment of a law to explain or clarify ambiguities in the language or the perceived meaning of that law (about Insanity Defense or other topics), or locating the current status of a bill and monitoring its progress.

    State Administrative Materials and Resources

    State regulations are rules and procedures promulgated by state agencies (which may apply to Insanity Defense and other topics); they are a binding source of law. In addition to promulgating regulations, state administrative boards and agencies often have judicial or quasi-judicial authority and may issue administrative decisions affecting Insanity Defense. Finding these decisions can be challenging. In many cases, researchers about Insanity Defense should check state agency web sites for their regulations, decisions, forms, and other information of interest.

    State rules and regulations are found in codes of regulations and administrative codes (official compilation of all rules and regulations, organized by subject matter). Search here:

    State opinions of the Attorney General (official written advisory opinions on issues of state law related to Insanity Defense when formerly requested by a designated government officer):

    Tools and Forms

    Law in Other Regions

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