Supreme Court Upholds Insanity Test Not Based on Knowing Right from Wrong

James Kahler shot his wife, her grandmother, and his two daughters after his wife filed for divorce and moved out with their children. He argued that Kansas “unconstitutionally abolished the insanity defense” by allowing the conviction of a mentally ill person “who cannot tell the difference between right and wrong.” The Supreme Court disagreed.

In Kahler v. Kansas the Supreme Court held 6-3 that the Constitution’s Due Process Clause does not require states to acquit defendants who, because of mental illness, could not tell right from wrong when committing their crimes.

While the Supreme Court describes four “strains” of the insanity defense which states have adopted the two most relevant to this case come from the landmark English case, M’Naghten (1843). In that case, the court stated two instances in which a mentally ill defendant was absolved of criminal culpability: if a mental illness left the person unable to understand what he or she was doing or to know that his or her actions were wrong.

Kansas has adopted the first prong of the M’Naghten rule requiring a defendant’s acquittal if the defendant is able to prove he or she lacked the mens rea (intent) to commit the crime due to mental illness. But in Kansas, unlike most states, a defendant may only argue that mental illness left him or her unable to know the difference between right and wrong after conviction to justify a reduced sentence or commitment to a mental health facility.

Per Supreme Court precedent a state rule about criminal liability violates due process only if it “offends some principle of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental.”

The Court, in an opinion written by Justice Kagan, held that the Due Process Clause does not require states to “adopt the moral-incapacity test from M’Naghten.” She described the historical record on the insanity defense as “complex—even messy.” She noted: “[e]arly commentators on the common law proposed various formulations of the insanity defense, with some favoring a morality inquiry and others a mens rea approach.” The Court concluded: “[n]o insanity rule in this country’s heritage or history was ever so settled as to tie a State’s hands centuries later.”

Justice Breyer, writing for himself and Justices Ginsburg and Sotomayor, read the history of the insanity defense differently. “Seven hundred years of Anglo-American legal history, together with basic principles long inherent in the nature of the criminal law itself, convince me that Kansas’ law “‘offends . . . principle[s] of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental.’”

Finally, the majority rejected Kahler’s characterization of Kansas abolishing the insanity defense entirely noting that Kansas “channels to sentencing, the mental health evidence that falls outside its intent-based insanity defense.” The dissent pushed back stating “our tradition demands that an insane defendant should not be found guilty in the first place. Moreover, the relief that Kansas offers, in the form of sentencing discretion and the possibility of commitment in lieu of incarceration, is a matter of judicial discretion, not of right.”

Four additional states—Alaska, Idaho, Montana, and Utah—"similarly exonerate a mentally ill defendant only when he [or she] cannot understand the nature of his [or her] actions and so cannot form the requisite mens rea.”