In Clark v. Arizona, 548 U. S. 735, this Court catalogued the diverse strains of the insanity defense that States have adopted to absolve mentally ill defendants of criminal culpability. Two—the cognitive and moral incapacity tests—appear as alternative pathways to acquittal in the landmark English ruling M’Naghten’s Case, 10 Cl. & Fin. 200, 8 Eng. Rep. 718. The moral incapacity test asks whether a defendant’s illness left him unable to distinguish right from wrong with respect to his criminal conduct. Respondent Kansas has adopted the cognitive incapacity test, which examines whether a defendant was able to understand what he was doing when he committed a crime. Specifically, under Kansas law a defendant may raise mental illness to show that he “lacked the culpable mental state required as an element of the offense charged,” Kan. Stat. Ann §21–5209. Kansas does not recognize any additional way that mental illness can produce an acquittal, although a defendant may use evidence of mental illness to argue for a lessened punishment at sentencing. See §§21– 6815©(1)©, 21–6625(a). In particular, Kansas does not recognize a moral-incapacity defense. Kansas charged petitioner James Kahler with capital murder after he shot and killed four family members. Prior to trial, he argued that Kansas’s insanity defense violates due process because it permits the State to convict a defendant whose mental illness prevented him from distinguishing right from wrong. The court disagreed and the jury returned a conviction. During the penalty phase, Kahler was free to raise any argument he wished that mental illness should mitigate his sentence, but the jury still imposed the death penalty. The Kansas Supreme Court rejected Kahler’s due process argument on appeal.
Held: 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. Pp. 6–24.
A state rule about criminal liability violates due process only if it “offends some principle of justice so rooted in the traditions and conscience our people as to be ranked as fundamental.” Leland v. Oregon, 343 U. S. 790, 798 (internal quotation marks omitted). History is the primary guide for this analysis. The due process standard sets a high bar, and a rule of criminal responsibility is unlikely to be sufficiently entrenched to bind all States to a single approach. As the Court explained in Powell v. Texas, 392 U. S. 514, the scope of criminal responsibility is animated by complex and ever-changing ideas that are best left to the States to evaluate and reevaluate over time. This principle applies with particular force in the context of the insanity defense, which also involves evolving understandings of mental illness. This Court has thus twice declined to constitutionalize a particular version of the insanity defense, see Leland, 343 U. S. 790; Clark, 548 U. S. 735, holding instead that a State’s “insanity rule[ ] is substantially open to state choice,” id., at 752. Pp. 6–9.
Against this backdrop, Kahler argues that Kansas has abolished the insanity defense—and, in particular, that it has impermissibly jettisoned the moral-incapacity approach. As a starting point, Kahler is correct that for hundreds of years jurists and judges have recognized that insanity can relieve criminal responsibility. But Kansas recognizes the same: Under Kansas law, mental illness is a defense to culpability if it prevented a defendant from forming the requisite criminal intent; a defendant is permitted to offer whatever evidence of mental health he deems relevant at sentencing; and a judge has discretion to replace a defendant’s prison term with commitment to a mental health facility.
So Kahler can prevail only by showing that due process requires States to adopt a specific test of insanity—namely, the moral-incapacity test. He cannot do so. Taken as a whole, the early common law cases and commentaries reveal no settled consensus favoring Kahler’s preferred right-from-wrong rule. Even after M’Naghten gained popularity in the 19th century, States continued to experiment with new approaches. Clark therefore declared: “History shows no deference to M’Naghten that could elevate its formula to the level of fundamental principle.” 548 U. S., at 749–752. The tapestry of approaches States have adopted shows that no single version of the insanity defense has become so ingrained in American law as to rank as “fundamental.” Id., at 749.
This result is not surprising. Ibid. The insanity defense sits at the juncture of medical views of mental illness and moral and legal theories of criminal culpability—two areas of conflict and change. Small wonder that no particular test of insanity has developed into a constitutional baseline. And it is not for the courts to insist on any single criterion moving forward. Defining the precise relationship between criminal culpability and mental illness requires balancing complex considerations, among them the workings of the brain, the purposes of criminal law, and the ideas of free will and responsibility. This balance should remain open to revision as new medical knowledge emerges and societal norms evolve. Thus—as the Court recognized previously in Leland, Powell, and Clark—the defense is a project for state governance, not constitutional law. Pp. 10–24.
307 Kan. 374, 410 P. 3d 105, affirmed.
KAGAN, J., delivered the opinion of the Court, in which ROBERTS, C. J., and THOMAS, ALITO, GORSUCH, and KAVANAUGH, JJ., joined. BREYER, J., filed a dissenting opinion, in which GINSBURG and SOTOMAYOR, JJ., joined.
A rather interesting approach to the long standing issue of the insanity defense. Going forward, clearly States will have a very wide latitude to define the insanity defense as they see fit. I am actually not surprised at all either by Kagan joining with the conservative wing or with her writing the Opinion of the Court in this case.
I have not fully digested the Opinion or the Dissent and I have not really decided as of yet where I stand on this. But it is something I wanted to elaborate on here, as it clearly is of major significance for criminal law.