Supreme Court Holds States Can Modify Insanity Defense


The Supreme Court held today in Kahler v. Kansas that the Constitution does not require states to use a definition of the insanity defense that “compels the acquittal of any defendant who, because of mental illness, could not tell right from wrong when committing his crime.”

Kansas law allows a defendant to invoke mental illness to show that he lacked intent for the crime. A defendant can also present evidence of mental illness after conviction to justify a reduced sentence or commitment to a mental health facility. But unlike in most other states, a defendant whose illness prevented him from recognizing his criminal act as morally wrong would not be acquitted in Kansas.

James Kahler argued that Kansas had “unconstitutionally abolished the insanity defense” by allowing the conviction of a mentally ill person “who cannot tell the difference between right and wrong.” He was sentenced to death in 2011 for the killing of his two daughters, his estranged wife, and his wife’s grandmother in 2009.

Mr. Kahler’s lawyers argued in their brief to the Supreme Court that the Kansas rule “defies a fundamental, centuries-old precept of our legal system: People cannot be punished for crimes for which they are not morally culpable.”

Justice Elena Kagan wrote for the Court that a state’s insanity defense violates the Due Process Clause only if it “offends some principle of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental.” In other words, she wrote, “The question is whether a rule of criminal responsibility is so old and venerable—so entrenched in the central values of our legal system—as to prevent a State from ever choosing another.”

The Court agreed with Mr. Kahler that a rule recognizing insanity as relieving responsibility for a crime is that type of fundamental rule. But it concluded that the rule adopted by Kansas and four other states—Alaska, Idaho, Montana and Utah—satisfies that broad principle because it allows a defendant to use mental health evidence to show their inability to form intent and to mitigate culpability and lessen punishment at sentencing.

Accordingly, the Court concluded, Kansas had not abolished the insanity defense entirely. And the Constitution doesn’t require it to adopt any specific rule because, the Court wrote, “No insanity rule in this country’s heritage or history was ever so settled as to tie a State’s hands centuries later.”

“Defining the precise relationship between criminal culpability and mental illness involves examining the workings of the brain, the purposes of the criminal law, the ideas of free will and responsibility,” Justice Kagan explained. “It is a project demanding hard choices among values, in a context replete with uncertainty, even at a single moment in time. And it is a project, if any is, that should be open to revision over time, as new medical knowledge emerges and as legal and moral norms evolve.”

“Which is all to say that it is a project for state governance, not constitutional law,” Justice Kagan concluded.

In a dissent joined by Justices Sonia Sotomayor and Ruth Bader Ginsburg, Justice Stephen Breyer wrote that requiring the acquittal of a defendant who could not tell right from wrong when committing his crime is a fundamental rule.

“Its basic insight is that mental illness may so impair a person’s mental capacities as to render him no more responsible for his actions than a young child or a wild animal,” he wrote. “Such a person is not properly the subject of the criminal law.” Kansas’s law, he reasoned, “excises this fundamental principle from its law entirely.”

He used a hypothetical to illustrate the deficiency in Kansas’s law: in Prosecution One, the defendant was shown at trial to have killed someone because they were convinced they were killing a dog; in Prosecution Two, the defendant killed someone out of the belief that a dog ordered them to. (Justice Breyer noted that mental illness is far more likely to cause the type of delusion in the second case than in the first.)

“Under Kansas’ changed law, the defendant in Prosecution One could defend against the charge by arguing that his mental illness prevented him from forming the mental state required for murder (intentional killing of a human being)—just as any defendant may attempt to rebut the State’s prima facie case for guilt,” Justice Breyer wrote. But the second defendant has no defense. “Because he acted with the requisite level of intent, he must be convicted regardless of any role his mental illness played in his conduct.”