The Reynal Law Firm, P.C.

(713) 228-5900

The Reynal Law Firm, P.C.

Does The Insanity Defense Carry A Constitutional Dimension?

  • By: The Reynal Law Firm, P.C
  • Published: March 19, 2019

Today (March 18, 2018), the Supreme Court granted cert in Kahler v. Kansas to consider whether the Eighth and Fourteenth Amendments allow states to eliminate the insanity defense.

At this time, Kansas and four other states (Alaska, Idaho, Montana, and Utah) do not recognize a defense to criminal liability involving mental disease precluding knowledge that an act was wrong. As the cert petition in this case explains, in Kansas, “Even a capital murder defendant need not be of sound mind. So long as he knowingly killed a human being—even if he did it because he believed the devil told him to, or because a delusion convinced him that his victim was trying to kill him, or because he lacked the ability to control his actions—he is guilty.”

Yet for centuries, our legal system has declined to punish people for crimes for which they are not morally culpable.

Kansas departed from the M’Naghten rule in 1996. Under the current rule, only in rare cases will even legally insane defendants actually lack the requisite mens rea based purely on a mental defect. The petitioner in Kahler has argued that this approach to criminal liability constitutes a constitutional violation because: 1) The Due Process Clause prohibits criminal liability that offends principles of justice so rooted in the traditions and conscience of the country as to be “fundamental”; and the Eighth Amendment bars criminal punishment that the common law condemned in 1789 or which violates fundamental human dignity, as reflected in contemporary values. As the Kahler petitioner points out, the insanity defense has deep roots in the Anglo-American legal tradition, and the majority of states have always permitted the defense.

Seven states recognize the insanity defense as constitutionally mandated. For example, the Nevada Supreme Court has said that the legislature may not abolish insanity as a complete defense to criminal liability. Nevada currently uses the M’Naghten rule. Other state courts have found it “too plain for argument” that defendants have been entitled to an insanity defense since before ratification of the Constitution.

In the five states that have abrogated the M’Naghten rule, with courts upholding statutes against constitutional challenges, the rulings have often come by a narrow vote over vigorous dissent. Four of these states have taken this approach even in death-penalty cases (Kansas, Idaho, Montana, and Utah).

As the Kahler petitioner points out, this issue carries the gravest considerations: one can certainly question whether a juror would be as likely to vote to kill a defendant who did not know their “murderous act” was wrong.

For centuries, our legal system has reserved criminal liability for people who can distinguish right from wrong. The Kahler petitioner has observed that the Supreme Court has said that it is a “humane” common-law principle that one cannot say a person deliberately intended to take life (and is thus not liable for murder) unless, at the time of the act, that person “had sufficient mind” to grasp the criminality or the right and wrong of the act. Justice Frankfurter said that “it has been a postulate of Western civilization that the taking of life by the hand of an insane person is not murder.”

Regarding the four traditional penological justifications for punishing criminal conduct, none would support a position abolishing the insanity defense. Retribution is not served by punishing those whose mental states are so distorted by a mental illness that their awareness of the crime and punishment has little or no relation to an understanding of those concepts as shared by the community. No deterrence value exists in punishing the insane because such punishment does not provide an example to others. Incarceration may incapacitate a mentally ill person for the duration of their sentence, but that person may remain unwell, and potentially dangerous, after the sentence ends. Prison does not serve to rehabilitate the mentally ill.

From a frequency perspective, one set of statistics has found that the insanity defense arises in about 1% of all felony cases . . . and that juries find about ¼ of those defendants “not responsible.”


The Reynal Law Firm, P.C. LLP is recognized as one of the State’s premier
criminal litigation firms. We bring a unique blend of talent,
tenacity and teamwork to every case we handle.