140 S. Ct. 1021 (2020)
In early 2009, Karen Kahler filed for divorce from James Kahler and moved out of their home with their two teenage daughters and nine-year-old son.1 Over the following months, James Kahler became more and more distraught.2
On Thanksgiving weekend, he drove to the home of Karen’s grandmother, where he knew his family was staying.3 Kahler entered through the back door and saw Karen and his son.4 He shot Karen twice, while allowing his son to flee the house.5 He then moved through the residence, shooting Karen’s grandmother and each of his daughters in turn.6 All four of his victims died.7
Kahler surrendered to the police the next day and was charged with capital murder.8 Before trial, Kahler filed a motion arguing that Kansas’s treatment of insanity claims violates the Fourteenth Amendment’s Due Process Clause.9 Kansas, he asserted, had unconstitutionally abolished the insanity defense by allowing the conviction of a mentally ill person who cannot tell the difference between right and wrong.10 The trial court denied the motion.11
At trial, Kahler attempted to show through psychiatric and other testimony that severe depression had prevented him from forming the intent to kill, but the court excluded that testimony consistent with Kansas law.12 The jury convicted Kahler of capital murder.13 During the penalty phase, the court permitted Kahler to offer additional evidence of his mental illness and to argue that it should mitigate his sentence, but the jury imposed the death penalty.14
Kahler appealed, challenging the constitutionality of Kansas’s approach to insanity claims.15 The Kansas Supreme Court rejected his argument and affirmed his convictions and sentence.16 The Supreme Court of the United States granted certiorari to review the case.17
Whether the Due Process Clause of the Fourteenth Amendment requires States to recognize an insanity defense that excuses criminal conduct because of a defendant’s inability to distinguish right from wrong?18
The Due Process Clause protects a defendant’s right to present a defense, but that right is subject to reasonable limitations.19 A state’s rule defining the circumstances under which a defendant may be held criminally responsible is unconstitutional only if it offends some principle of justice so rooted in the traditions and conscience of our people as to be ranked as fundamental.20
No. Kansas law channels evidence of mental illness solely into the question of whether the defendant formed the requisite mens rea and permits such evidence at sentencing to mitigate punishment.21 This approach does not violate due process.
Kahler was charged with capital murder after killing four family members during a domestic dispute.22 He sought to introduce expert testimony that major depressive disorder prevented him from forming the intent required for first-degree murder.23 The trial court excluded broader evidence of moral incapacity consistent with Kansas statute.24 The jury convicted Kahler on all counts and imposed the death penalty after hearing additional mental health evidence at sentencing.25 The Kansas Supreme Court affirmed.26
History reveals no single formulation of the insanity defense that qualifies as fundamental.27 Jurisdictions have long varied between cognitive incapacity tests, moral incapacity tests, irresistible impulse tests, and product tests.28 Some states, like Kansas, have eliminated any separate insanity defense beyond negating mens rea.29 Prior decisions confirm that states retain leeway to define the defense, as the Court upheld variations in Leland v. Oregon and Clark v. Arizona.30
The Due Process Clause does not require States to recognize an insanity defense that excuses criminal conduct because of a defendant’s inability to distinguish right from wrong.31
Related opinions on this issue
Joined by Justices Ginsburg And Sotomayor
Justice Breyer dissented.32 He maintained that the moral incapacity component of the insanity defense is deeply rooted in Anglo-American legal tradition and therefore fundamental to due process.33 For centuries the common law recognized that a person who cannot distinguish right from wrong because of mental illness should not be held criminally responsible.34
Kansas’s decision to eliminate this defense is an outlier among the states.35 The near-universal acceptance of some form of the traditional insanity defense supports its fundamental status.36 Breyer distinguished Clark v. Arizona as addressing only whether a state could channel mental illness evidence into a limited insanity defense while still retaining the defense itself.37
He concluded that due process requires states to provide an insanity defense excusing conduct when mental illness prevents distinguishing right from wrong.38