Kansas permits defendants to raise an insanity defense based on whether the defendant “lacked the culpable mental state required as an element of the offense charged.” James Kahler, who was charged with capital murder for killing four family members, argued that he should have been able to raise an insanity defense based on whether he had a mental illness that prevented him from distinguishing right from wrong, and Kansas’ failure to allow that version of the defense violated due process. The Kansas Supreme Court denied Kahler relief.

The Court, in a 6-3 ruling authored by Justice Kagan, affirmed, holding that the historical backdrop of the insanity defense did not require that States incorporate a moral-incapacity test into the insanity defense. The majority recognized that changing views of insanity required that States be the ones to properly define it, and not the Court. Justice Breyer, joined by Justices Ginsburg and Sotomayor, dissented, arguing that Kansas’ version of the insanity defense gutted a core component of the defense. A link to the opinion in Kahler v. Kansas is here.