Eric Roytman

Document Type

Supreme Court Commentaries

Publication Date



Kahler v. Kansas, Eighth Amendment, insanity defense, criminal law

Subject Category

Constitutional Law


In 1995, Kansas, along with a small number of other states, passed a statute abrogating the widely recognized common law insanity defense. At common law, a defendant could raise the defense when a mental illness impaired his ability to distinguish right from wrong, allowing him to escape liability even when the elements of the crime were otherwise fulfilled. However, under Kansas’ statutory scheme, evidence of a defendant’s mental illness can only be used to negate the mens rea element of the offense. In other words, evidence of mental illness is only relevant when it shows that the defendant lacked the intent to commit the act itself, regardless of whether he believed that act was moral. In Kansas, a defendant driven by mental illness to intentionally harm another has no viable path to acquittal at trial, even when his mental illness caused him to believe his actions were morally right. In Kahler v. Kansas, the Supreme Court will consider the constitutionality of Kansas’s statutory scheme. The Court’s decision in this case will have profound implications for how courts deal with defendants struggling with mental illness. A decision to uphold Kansas’s statute could be interpreted as a green light for other states to abolish a right that was firmly entrenched in common law long before the Court even existed. This commentary will analyze Kansas’s statute in light of the Petitioner’s Due Process and Eighth Amendment challenges. Doing so requires examining the origins of the insanity defense and the importance of moral capacity in the American criminal justice system. This commentary will argue that (1) Kansas’s statute is unconstitutional because the Due Process Clause proscribes state governments from assigning criminal liability to defendants who cannot differentiate right from wrong; and (2) the Eighth Amendment does not apply to the statute at issue in this case.