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Kahler v. Kansas: Narrowing the Insanity Defense

April 1, 2020


Kahler v. Kansas, 589 U.S. ___ (2020) (Kagan, J.).
Response by Laird Kirkpatrick
Geo. Wash. L. Rev. On the Docket (Oct. Term 2019)
Slip Opinion | SCOTUSblog

Kahler v. Kansas: Narrowing the Insanity Defense

A fundamental pillar of the Anglo-American criminal justice system for centuries has been its supposed ability to distinguish between the “bad and the mad” by recognition of a well-established insanity defense. That pillar has been badly shaken by the United States Supreme Court’s recent decision in Kahler v. Kansas.1 Kansas allows evidence of insanity at trial only to show that the defendant lacked the mens rea of the charged crime. Kahler argued that the Kansas statute violated the Due Process Clause by failing to recognize a defense where an accused was so mentally ill that he did not realize his conduct was wrongful. The Supreme Court, in a 6-3 decision written by Justice Kagan, rejected his claim and affirmed his death sentence for murdering four members of his family. Justice Breyer filed a dissenting opinion, joined by Justices Sotomayor and Ginsburg.

Some commentators had viewed Kahler as posing the question whether a state may abolish the insanity defense entirely. The Kansas statute did not go that far. The mens rea approach meant that Kansas largely adopted the first prong of the famous M’Naghten standard, which held: “[T]o 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, [1] as not to know the nature and quality of the act he was doing; or, [2] if he did know it, that he did not know he was doing what was wrong.”2 It did not adopt the second prong—that the accused appreciated the wrongfulness of his conduct. Thus, under Kansas law, if a mentally ill defendant had killed a person believing him to be a space alien, he would have a defense. If he had killed a person as a result of a paranoid-schizophrenic delusion that the victim was an agent of the Devil about to injure his children, he would not have a defense.

The majority opinion begins by commenting that “a state rule about criminal liability . . . violates due process only if it ‘offends some principle of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental’”3 and that “[the Court’s] primary guide in applying that standard is ‘historical practice.’”4 The majority was not persuaded by the historical fact that 45 States, the Federal Government, and the District of Columbia have all adopted insanity defenses broader than Kansas by “retain[ing] some inquiry into the blameworthiness of the accused.”5 Only four other states have eliminated the knowledge of wrongfulness inquiry and attempted to repeal or cut back the insanity defense in a manner similar to Kansas. The Court determined that this overwhelming majority did not demonstrate “historical practice,” because of the diversity in the wording of the standards among states. The Court discounted the fact that much of the diversity is attributable to the fact that many states have chosen to build upon M’Naghten, not to narrow it. The Court also noted that some states have limited the second prong of M’Naghten to showing lack of knowledge that the conduct was legally wrong rather than morally wrong. But such states are still requiring an inquiry into knowledge of wrongfulness before an accused claiming an insanity defense can be convicted, and that is an inquiry not allowed in Kansas.

The majority seemed to view the case as relatively simple, because the Court has never required a single formulation of the insanity defense as a matter of constitutional law. In Clark v. Arizona,6 the Court approved a state statute that adopted only the second prong of M’Naghten (knowledge of wrongfulness) but not the first prong (cognitive ability). If the first prong can be constitutionally eliminated, why not the second? One answer is found in Clark itself where the Court recognized that evidence a defendant might offer to prove the second prong “is both relevant and admissible” with respect to the first prong, because “if a defendant did not know what he was doing when he acted, he could not have known that he was performing the wrongful act charged.”7 Thus, under the Arizona statute, a defendant is allowed to offer evidence bearing on both prongs. Under the Kansas statute, only evidence bearing on the first prong (mens rea) is permitted, and evidence bearing on the second prong (knowledge of wrongfulness) is barred. Consequently, Kahler will have far more impact than Clark in limiting the ability of an accused to assert an insanity defense.

Even more importantly, as the extensive research cited in the dissent reveals, cases where the insanity defense is used only to rebut mens rea are relatively rare. In the majority of cases where the insanity defense is asserted, the defendant is aware of and intends his conduct. The insanity defense is used to explain what type of mental illness motivated the accused to engage in such conduct, often as the result of a psychic break, hallucination, or paranoid delusion. The defendant in such cases, because of his insanity, often believes that he is acting to save family members or others from some type of terrible imagined harm, and therefore is not acting with malevolent motives. As the dissent commented, the Kansas statute thus “requires conviction of a broad swath of defendants who are obviously insane and would be adjudged not guilty under any traditional form of the defense. This result offends deeply entrenched and widely recognized moral principles underpinning our criminal laws.”8 By approving the exclusion of the type of evidence most commonly used to establish an insanity defense, Kahler represents a significant narrowing of an accused’s right to assert an insanity defense.

The most troubling aspect of Kahler is that it raises the question whether there even is a constitutional right to assert an insanity defense. Could a state now abolish both prongs of the M’Naghten standard (or any variants thereof)? Could a state reject any formulation of an insanity defense and bar evidence of insanity at trial entirely? Surely not, for the same reasons that barring evidence of self-defense or similar traditional defenses would raise serious constitutional issues. But the Court gives little reassurance on this point. The majority opinion concludes by saying that “[d]efining the precise relationship between criminal culpability and mental illness . . . is a project for state governance, not constitutional law.”9 In justifying its remarkable deference to state legislatures on this point, the Court set forth an optimistic vision of state legislatures as policy making laboratories, carefully considering the difficult choices involved in formulating the insanity standard, including, “examining the workings of the brain,”10 as well as “new medical knowledge”11 and engaging in “reasonable debate about what the cognate legal and medical tests should be.”12 The leading article examining how the Kansas statute was actually enacted gives no support whatsoever to this rosy vision.13 In reality, attempts to narrow or repeal the insanity defense are more commonly a result of “get tough on crime” initiatives rather than deliberative and reasoned legislative debate. Such initiatives are often made in response to a sensational crime where the insanity defense was raised.

The mentally ill are perhaps the least powerful minority group in the country. They have virtually no ability to stand up to legislative action taken in response to public passion and fear, even when that fear is based on misinformation and misconceptions. If any citizens deserve judicial oversight of legislative actions which deprive them of a protection that has been recognized for centuries, it would seem that they qualify. When the Court says in Kahler that the insanity rule “is substantially open to state choice,”14 it is to be hoped that by “substantially” the Court doesn’t mean “totally.” And when the Court says the development of the insanity standard “is a project for state governance, not constitutional law,”15 it can only be hoped that this does not mean total abdication of the Court’s role in protecting the due process rights of all citizens.


Laird Kirkpatrick is the Louis Harkey Mayo Research Professor at The George Washington University Law School. He is coauthor of the five-volume treatise Federal Evidence (4th ed. Thomson West, 2013), as well as several other books. He is a former federal prosecutor and previously served as Counsel to the head of the Criminal Division of the U.S. Department of Justice and as a member of the United States Sentencing Commission. He also served on the Advisory Committee on Criminal Rules and the Advisory Committee on Evidence for the United States Judicial Conference. He is past chair of the Evidence Section of the American Association of Law Schools, an elected member of the American Law Institute, and a life fellow of the American Bar Foundation.


  1. No. 18-6135, (U.S. Mar. 23, 2020).
  2. M’Naghten’s Case, 10 Cl. & Fin. 200, 210, 8 Eng. Rep. 718, 722 (H.L. 1843).
  3. Kahler, slip op. at 6 (quoting Leland v. Oregon, 343 U.S. 790, 798 (1952)).
  4. Id. (quoting Montana v. Egelhoff, 518 U.S. 37, 43 (1996) (Scalia, J., plurality opinion)).
  5. Id. at 16 (Breyer, J., dissenting).
  6. 548 U.S. 735 (2006).
  7. Id. at 753.
  8. Kahler, slip op. at 21 (Breyer, J., dissenting).
  9. Id. at 24 (majority opinion).
  10. Id.
  11. Id.
  12. Id. (quoting Clark, 548 U.S. at 752–53).
  13. See Marc Rosen, Insanity Denied: Abolition of the Insanity Defense in Kansas, 8 Kan. J.L. & Pub. Pol’y 253, 254, 262 (1999) (concluding that the adoption of Kansas’s statute was based on “political cynicism,” public fear, and misconceptions about how often the insanity defense is asserted and how rarely it is successful).
  14. Kahler, slip op. at 9 (quoting Clark, 548 U.S. at 752).
  15. Id. at 24.

Recommended Citation
Laird Kirkpatrick, Response, Kahler v. Kansas: Narrowing the Insanity DefenseGeo. Wash. L. Rev. On the Docket (Apr. 1, 2020), https://www.gwlr.org/kahler-v-kansas-narrowing-the-insanity-defense/.

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