Does the Constitution Require States to Provide an Insanity Defense to Defendants in Criminal Proceedings?

“Dec 07 007”by beerimoalem is licensed under CC BY-NC-SA 2.0

Margo Brandenburg, Associate Member, University of Cincinnati Law Review

I. Introduction 

American courts have historically reserved criminal punishment for morally culpable defendants.[1] Dating back to the English legal system, a deeply ingrained principle of American criminal jurisprudence has been that those without moral culpability should be excused from legal punishment.[2] With this in mind, courts around the country adopted the insanity defense to reflect this tradition that excuses individuals who are unable to tell whether their act was right or wrong.[3]                                                 

Today, this deeply ingrained principle of criminal law is being called into question. This month, the Supreme Court will listen to arguments about whether the Eighth and Fourteenth Amendments permit states to abolish the insanity defense in Kahler v. Kansas.[4] Part II of this article discusses the history of the insanity defense in the United States and how it is used today. Part III addresses the background and arguments posed in Kahler. Part IV argues that states should be constitutionally permitted to create an alternative method from the traditional insanity defense. Part V concludes that allowing the states to determine their own criminal laws is the proper policy decision.  

II. The Insanity Defense: Then and Now

Criminal laws are not uniform in the United States. There is no national consensus on the law that governs the standards of using the insanity defense.[5] Each state, the District of Columbia, and the federal system developed their own unique set of criminal laws.[6] With this in mind, this section will focus on the relevant laws of the majority of the United States. 

A. The Insanity Defense Through History

The insanity defense is known to be a staple throughout every jurisdiction in the history of the United States.[7] Traditionally, it was affirmatively pleaded as a defense by a criminal defendant that bore the burden of persuasion.[8] The standard for the defense of insanity has not been uniform in its formulation, but every jurisdiction throughout the country has recognized some form of an insanity defense in criminal proceedings in the past.[9]

States that provide the insanity defense today generally follow some version of the two-part M’Naghten rule.[10] Also known as the “right and wrong” test, the M’Naghten rule provides that a defendant should not be held criminally liable if he does not know the nature of his act, or if he does not know right from wrong with respect to the act.[11] Under this rule, the defense must prove that at the time of the criminal act, the accused did not know his actions were contrary to the law.[12]

The insanity defense was forced into spotlight after John Hinckley Jr.’s attempted assassination of then-President Ronald Reagan on March 30, 1981.[13] After the verdict of not guilty by reason of insanity came out, public suspicion exploded over the use of the insanity defense in criminal proceedings.[14] Hinckley’s acquittal outraged the American public, not only due to his thin record of dealing with mental illness, but also because of his calculated efforts in committing the crime.[15] Even today, decades after the Hinckley verdict, lawyers witness the ruling’s effect on the insanity defense. The chances of a defendant being acquitted by reason of insanity are slim and the threshold is high.[16] The public’s hostile feelings toward the insanity defense has led states to create legislation that reflects this disproval.[17]

B. Changing Times for The Insanity Defense 

Since the Hinckley case, four states around the country have essentially abolished a criminal defendant’s ability to plead insanity as a defense to a crime: Idaho, Montana, Utah, and Kansas.[18] Thus, if the Court decides that states may adopt alternative methods for looking at a defendant’s mental state, the majority of states around the country that currently use the insanity defense may begin reconsidering their laws. States have not uniformly replaced the insanity defense, but one alternative method states adopted is the “mens rea approach.”[19] The mens rea approach allows evidence in to attest to a defendant’s mental disease or defect as it effects the mental element of the crime.[20] Accordingly, this approach does away with the ability of a defendant to show a lack of understanding of right from wrong as a defense to the prima facie case.[21]

C. The Question Left Unanswered by Clark v. Arizona[22]

It is undetermined whether the Constitution allows states to abolish the traditional insanity defense and replace it with another method to evaluate a defendant’s culpability. The Supreme Court addressed this question briefly in Clark.[23] In Clark, a man killed a police officer in the line of duty and was sentenced to life in prison.[24] The man argued that Arizona’s insanity test violated the Fourteenth Amendment’s due process clause because it impermissibly excluded the first portion of the two-part M’Naghten test.[25] In response, the Supreme Court explained that although seventeen states and the federal government had adopted versions of the M’Naghten test, the M’Naghten test was not the only standard that comports with due process.[26] In addition, the Court stated that no particular formulation had yet evolved into a baseline for due process, and that rules regarding insanity should be left to state choice.[27] The Court went on to say that it has “never held that the Constitution mandates an insanity defense, nor has it held that the Constitution requires one.”[28] Because, in the Court’s opinion, the case did not call for an evaluation of the issue of the insanity defense, the Court did not discuss the issue.[29]

III. Kahler v. Kansas[30]

A. Background 

On November 28, 2009, James Kraig Kahler killed four of his family members including his wife, two children, and his wife’s grandmother, after breaking into his wife’s grandmother’s home in Kansas.[31] The state charged him with one count of capital murder, or, in the alternative, four counts of first-degree murder, and one count of aggravated burglary.[32] In the district court, the defense did not dispute that Kahler had murdered his family members.[33] Instead, the defense asserted that due to Kahler’s severe depression during the time of the crime, Kahler was incapable of forming the intent and premeditation required to establish capital murder.[34] Testimony from a forensic psychiatrist confirmed that Kahler’s depression and his capacity to manage his own behavior had been so decreased that he could not refrain from committing the act.[35] Even given this evidence, the jury convicted Kahler of aggravated burglary and capital murder, and sentenced him to death.[36]

Kahler appealed his case to the Kansas Supreme Court, where he questioned the constitutionality of a Kansas statute that provides “[i]t is a defense to a prosecution under any statute that the defendant, as a result of disease or defect, lacked the mental state required as an element of the offense charged. Mental disease or defect is not otherwise a defense.”[37] Specifically, Kahler argued that this statute violated the due process rights of defendants because it offends a principle of justice that is so important that it is fundamental.[38] The Kansas statute is Kansas’s version of the mens rea approach to determining criminal liability.[39] Kansas replaced the M’Naghten rule with the mens rea approach in 1996.[40] The Kansas Supreme Court stated that it already determined that Kansas’s mens rea approach does not offend due process under either the United States or Kansas constitutions, so the court would not consider the argument again.[41] The Kansas Supreme Court then affirmed the ruling of the district court.[42] Kahler appealed the decision again, this time to the Supreme Court of the United States.

B. Kahler’s Arguments 

To the Supreme Court of the United States, Kahler’s brief framed the question presented as whether states are permitted to abolish the insanity defense.[43] In short, Kahler’s most noteworthy arguments were that Kansas’s lack of an insanity defense violates the Fourteenth Amendment’s due process clause and the Eighth Amendment’s restriction on cruel and unusual punishment.[44]

1. Fourteenth Amendment

Kahler articulated that the insanity defense should be preserved within the states because it is so rooted in our nation’s history that the defense became a fundamental right that cannot be taken away without the due process of law.[45] Kahler deep-dove into the history of the insanity defense around the country to show that the defense should not be abolished because it represents a deeply ingrained principle of American criminal jurisprudence – that moral blameworthiness is the prerequisite for criminal punishment.[46]

2. Eighth Amendment

In the next part of his brief, Kahler argued that Kansas’s mens rea approach is in violation of the Constitution because there is no punishment more cruel and unusual than one asserted on someone who is unable to understand the nature of his wrongdoing.[47] Noting that the Court’s Eighth Amendment jurisprudence has historically centered around cruel punishment, Kahler cited Robinson v. California, where the Court used the Eighth Amendment to prohibit a criminal conviction.[48] Kahler’s Eighth Amendment argument was based on the conclusion that punishing the insane does not advance any goals of the current criminal law system.[49]

3. Validity of the Mens Rea Approach

Kahler argued against the validity of the mens rea approach as a mechanism for excusing morally blameless individuals.[50] He asserted that the mens rea approach does not account for an individual who intends to perform a criminal act, but may not have the capacity to understand that the criminal act is wrong.[51] As a result, Kahler argues that the insanity defense covers more ground than the mens rea approach – mentally incapacitated individuals are more likely to get excused for their criminal activity when they are able to plead insanity. [52]

C. Kansas’s Arguments

Kansas framed the issue very differently than Kahler, saying that the state has not “abolished” the insanity defense, but rather, it has “redefined” the defense to adopt a mens rea approach instead.[53]

1. Fourteenth Amendment

Counsel for Kansas argued that the mens rea approach does not violate the due process clause of the Fourteenth Amendment.[54] In support of this argument, Kansas asserted that the insanity defense is not rooted in our nation’s history.[55] In fact, Kansas noted that the insanity defense does not enjoy widespread use or acceptance in any capacity – the utilization of the defense has not been uniform in its formulation throughout history.[56] To add to this, Kansas asserted that due process does not require a particular insanity test, as noted by the Clark decision.[57] Lastly, Kansas argued that because an individual does not believe the crime they committed was wrong does not make them blameless.[58] Kansas posed an example of someone killing an abortion doctor because the person believes that abortions are wrong.[59] Even if that individual believes the killing of the abortion doctor was justified, they are not morally blameless, and should not escape criminal prosecution.[60]

2. Eighth Amendment 

Kansas also argued that the mens rea approach to insanity is constitutional under the Eighth Amendment. First, Kansas argued that Kahler’s claim is not properly before the Court because Kahler did not bring the Eighth Amendment claim to the Kansas Supreme Court.[61] Even on the merits, Kansas asserted that convicting individuals who do not realize their criminal actions are wrong does not constitute cruel and unusual punishment.[62] Specifically, Kansas argued that the history of the Eighth Amendment was to protect against cruel and unusual punishments, and stretching the Amendment to reach affirmative defenses invades on a state’s ability to define its own criminal laws.[63]

3. Attack on Kahler’s Insanity 

Lastly, Kansas argued that even the right and wrong test would not rid Kahler of liability for his actions because he was not insane at the time he murdered his family.[64] According to Kansas, Kahler was a calculated, cold-blooded killer, as evidenced by the jury’s finding that he should be condemned to death.[65] Due to this, Kansas asserted that even if Kahler was presented with the ability to use the insanity defense, he would not be relieved of punishment.[66] As a result, Kansas asserted that Kahler’s death sentence should be affirmed by the Court.[67]

IV. Discussion  

Kansas’s version of the mens rea approach allows a specific group of defendants who believe they are justified in committing the crime to be sent to prison even if they have a mental illness. For example, if a person is in a grocery store check-out and they think that the shopper in front of them is a bug and punches the shopper to death, they would not have the mens rea to commit a crime because they did not intend to commit murder –  they thought that person was just a bug. On the other hand, if a person is having hallucinations and thinks that the shopper in front of them in the grocery store is a terrorist and subsequently strangles the shopper to death, the person still has the requisite mens rea to commit the crime of murder. In this case, the insane person would think that they were justified in committing the murder. This person, who truly believes they were justified in murdering, likely would be sent to prison in a state that has adopted the mens rea approach. In a state that utilizes the insanity defense, however, the person may have a viable chance to be found not guilty by reason of insanity. Kansas’s version of the mens rea approach is potentially problematic for the mentally ill people who get sent to prison in a state following the mens rea approach. These individuals are less likely to get the sufficient mental health medical attention in a prison system.[68]

While some individuals who cannot tell right from wrong should be institutionalized rather than imprisoned, it is a stretch to say that knowledge of wrongfulness is a necessity when it comes to declaring someone mentally insane. Individuals who murder people, believing that the murder is justified, are not all innocent. A murderer should not be let off scot-free just because they have some kind of illness on the side; in order to be found not guilty by reason of insanity, the person must have murdered because of his mental illness. The mens rea approach effectively encompasses this reasoning, ensuring that only those who are truly blameless get medical attention. 

Although Kansas’s approach to determining insanity may not perfect, the Supreme Court should still defer to individual state’s judgment in adopting criminal laws and determining who should be deemed blameless. As evidenced by Clark, the affirmatively pleaded insanity defense is not a requirement to preserve a defendant’s due process rights. Thus, a state is not violating due process rights when it replaces the traditional insanity defense with another method like the mens rea approach. Even if the insanity defense is rooted in our history, evidence of a defendant’s mental state is not lost using the mens rea approach. Under the mens rea approach, evidence of insanity may still be brought in to attest to the defendant’s mental state at the time of the crime, but during a different point in the court proceeding. Thus, individuals are not losing their right to present an argument that they are insane. In effect, the Court should find that there has been no Fourteenth Amendment violation by Kansas’s adoption of the mens rea approach. 

Kahler’s Eighth Amendment claim is unconvincing. The Eighth Amendment protects against cruel and unusual punishments. The Court should not to get into the nit-picking of whether each individual criminal defendant’s punishment was a violation of the Eighth Amendment. If the Court were to do so, it would be wrongfully invading on state court’s right to interpret criminal laws within the state. Additionally, the Supreme Court has recognized the longstanding deference to the states in determining the extent to which mental illness may excuse liability for a crime.[69]

V. Conclusion 

The Supreme Court should find that, given the sound arguments presented by Kansas and other public policy considerations, the ruling of the Kansas Supreme Court should be affirmed in Kahler. A ruling affirming the Kansas Supreme Court will likely prompt many states to reconsider their use of the insanity defense, and possibly reformulate their laws to model something like Kansas’s mens rea approach.[70] Regardless of the downsides of the mens rea approach that Kansas has adopted, Kansas has not violated any constitutional principles by moving away from the traditional insanity defense. Given the wide deference given to states to determine criminal responsibility, Kansas has properly used its discretion in deciding to allow evidence of insanity to attest to the mens rea of the crime committed. As discussed, the traditional principle that morally blameless individuals should not be criminally punished is one of the highest values in criminal law. Kansas has showed us that this traditional principle of American law can still be preserved even if alternative methods are used to determine a defendant’s mental state at the time of a crime. 

[1]Brief for The American Bar Association as Amicus Curiae Supporting Petitioner at 5, Kahler v. Kansas, (No. 18-6135), US. S. Ct. Briefs LEXIS 2132 at *5. 



[4]No. 18-6135 (petition for cert. filed Sep. 28, 2018).


[6]Robinson, Paul H. and Williams, Tyler Scot, “Mapping American Criminal Law Variations Across the 50 States: Ch. 14 Insanity Defense” (2017). Faculty Scholarship. 1718.

[7]Daniel J. Nusbaum, Note, The Craziest Reform of Them All: A Critical Analysis of the Constitutional Implications of “Abolishing” The Insanity Defense, 87 Cornell L. Rev. 1509, 1517 (2002). 


[9]Robinson & Williams, supra note 6.

[10]Stephen P. Garvey, Agency and Insanity, 66 Buffalo L. Rev. 123, 127 (2018).

[11]State v. Kahler, 410 P.3d 105, 125 (2018) (quoting State v. Baker, 819 P.2d 1173 (1991)). 


[13]Natalie Jacewicz, After Hinckley, States Tightened Use of The Insanity Plea (Jul. 28, 2016, 10:20 AM),


[15]Jennifer S. Bard, Re-arranging Deck Chairs on the Titanic: Why the Incarceration of Individuals with Serious Mental Illness Violates Public Health, Ethical, and Constitutional Principles and Therefore Cannot Be Made Right by Piecemeal Changes to the Insanity Defense, 5 Hous. J. Health L. & Pol’y 1, 34 (2005). 


[17]Brief for The American Bar Association as Amicus Curiae Supporting Petitioner at 5, Kahler v. Kansas, (No. 18-6135), US. S. Ct. Briefs LEXIS 2132 at *5.

[18]Daniel J. Nusbaum, Note, The Craziest Reform of Them All: A Critical Analysis of the Constitutional Implications of “Abolishing” The Insanity Defense, 87 Cornell L. Rev. 1509, 1515 (2002). 

[19]State v. Kahler, 410 P.3d 105, 125 (2018). 

[20]Id. (citing State v. Jorrick, 4P.3d 610 (2000)).


[22]548 U.S. 735 (2006).


[24] 743.

[25]Id. at 746. 

[26]Clark v. Arizona, 548 U.S. 735, 752 (2006).


[28] 752 n.20 (2006).


[30](No. 18-6135) (petition for cert. filed Sep. 28, 2018).

[31]State v. Kahler, 410 P.3d 105, 114 (2018).

[32]Id. at 113.

[33]Id. at 114.



[36]Id. at 124. 


[38]Id. at 125.

[39]Id. at 125. 


[41]Id. (citing State v. Bethel, 66 P.3d 840 (2003)).

[42]State v. Kahler, 410 P.3d 105, 112 (2018).

[43]Brief for Petitioner at i, Kahler v. Kansas, (No. 18-6135) 2019 U.S. S. Ct. Briefs LEXIS 2056 at *10. 

[44] Brief for Petitioner at 2, Kahler v. Kansas, (No. 18-6135) 2019 U.S. S. Ct. Briefs LEXIS 2056 at *10.

[45]Id. at 16. 

[46]Id. at 14.

[47]Id. at 29.

[48]Id. (citing Robinson v. California, 370 U.S. 660, 667 (1962) (holding that conviction for the status of being a drug addict is an Eighth Amendment violation)).  

[49]Id. at 33-35. (Discussing why punishing insane people does not advance criminal law values of retribution, deterrence, incapacitation, or rehabilitation). 

[50]Brief for Petitioner at 40, Kahler v. Kansas, (No. 18-6135), 2019 U.S. S. Ct. Briefs LEXIS 2056 at *70.

[51]Id. at 41. 


[53]Brief for Respondent at 8, Kahler v. Kansas, (No. 18-6135), 2019 U.S. S. Ct. Briefs LEXIS 2974 at *16. 

[54]Id. at 18.  


[56]Id. (citing Clark v. Arizona, 548 U.S. 735, 749 (2006)).

[57]Brief for Respondent at 19, Kahler v. Kansas, (No. 18-6135), 2019 U.S. S. Ct. Briefs LEXIS 2974 at *39.

[58]Id. at 40.

[59]Id. at 41.


[61]Id. at 46-47.

[62]Brief for Respondent at 47, Kahler v. Kansas, (No. 18-6135), 2019 U.S. S. Ct. Briefs LEXIS 2974 at *60-61

[63]Id. at 47-48. (citing Clark v. Arizona, 548 U.S. 735, 749 (2006)).

[64]Id. at 55. 

[65]Brief for Respondent at 56, Kahler v. Kansas, (No. 18-6135), 2019 U.S. S. Ct. Briefs LEXIS 2974 at *25-26. 


[67]Id. at 57.

[68]Christina Canales, Note, Prisons: The New Mental Health System, 44 Conn. L. Rev.1725, 1748 (2012).

[69]Brief for Respondent at 15 n.3, Kahler v. Kansas, (No. 18-6135), 2019 U.S. S. Ct. Briefs LEXIS 2974 at *24. (citing Brief of the United States as Amicus Curiae, Clark v. Arizona, 548 U.S. 735 (2006) (No. 05-5966), 2006 WL 542415, at *9-10).

[70]Amy Howe, Argument preview: Justices to hear challenge to lack of insanity defense, SCOTUSblog (Sep. 30, 2019, 4:18 PM),

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