Kahler v. Kansas

In a 6-3 decision, the Supreme Court determined that due process does not require Kansas to adopt an insanity test that turns on a defendant’s ability to recognize that his crime was morally wrong.

The Court acknowledged that for hundreds of years, judges have recognized that a criminal defendant’s insanity at the time of the commission of a criminal act can relieve criminal responsibility. And while the Kansas law at issue does make irrelevant the question of moral incapacity, it still permits mental illness as a defense to culpability if it prevented a defendant from forming the criminal intent required for commission of the crime. The Court has repeatedly declined to adopt one particular version of the insanity defense, and it declined to do so in this case, as well. No single version of the insanity defense has become so ingrained in American law as to be “fundamental,” and states retain the authority to define the precise relationship between criminal culpability and mental illness.

Justice Stephen Breyer wrote a dissenting opinion, in which Justices Ruth Bader Ginsburg and Sonia Sotomayor joined. Justice Breyer argued that Kansas did not merely redefine the insanity defense; it “eliminated the core” of a defense “so rooted in the traditions and conscience of our people as to be ranked as fundamental.” He provided several hypotheticals to illustrate his point that Kansas’s version of the insanity defense “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.” As such, he would conclude that Kansas’s law violates a “fundamental precept of our criminal law” and thus is unconstitutional.

https://www.oyez.org/cases/2019/18-6135