Kahler v. Kansas and the Constitutionality of the Mens Rea Approach to Insanity

In 1995, the Kansas legislature adopted what is referred to as the "mens rea approach" and abolished the affirmative insanity defense. This approach allows a defendant to be acquitted who lacks the requisite mental state for the crime, without consideration of the defendant's understanding of wrongfulness. In Kahler v. Kansas, the U.S. Supreme Court recently held that this restrictive approach does not violate due process and that a state is not required to adopt an insanity test which considers a defendant's moral capacity at the time of the crime. Four other states currently follow the mens rea approach, or some form of it. In this article, we first discuss a brief history of insanity defense laws in the United States. We then outline relevant legislative history and precedent in Kansas and other states that have adopted the mens rea approach. We next discuss the Supreme Court's reasoning in Kahler The significance of this test is further discussed, including Eighth Amendment considerations. We advocate for continued education of the public, legislators, and the judiciary regarding the use, application, and necessity of an affirmative insanity defense.