Out of Sight and Out of Mind:Supreme Court Arguments on the Insanity Defense Reveal Criminal Law’s Disguised Moral Culpability Requirement

This article unmasks a hidden lesson for criminal law scholars in the Supreme Court’s March decision in Kahler v. Kansas—a ruling that rejected the petitioner’s claim that due process precluded Kansas from abolishing the right-and-wrong test of insanity. I contend that petitioner and the dissenting justices identified solid evidence that the test is the modern continuation of an age-old moral culpability requirement in common law criminal doctrine. The writers of leading treatises do not recognize a moral culpability requirement among the canonical premises of criminal law; most philosophers of the criminal law would concur that current law lacks one; but those same philosophers would also hold that there should be one. This conventional wisdom is in error. Considering the historical evidence marshaled in Kahler, my thesis is that the list of canonical premises should be augmented to include moral culpability alongside others like voluntariness, mens rea, and ex ante criminalization. Moral culpability is a basic premise of criminal liability in every criminal case. It is ordinarily assumed, but it can be negated when a defendant successfully argues that he was unable to appreciate the wrongness of his actions due to mental disease or defect. In this regard, it is much like the well-recognized voluntariness requirement: voluntariness is rarely an issue in criminal law cases and need not be specially proven unless there are special circumstances (usually physical or psychological abnormality, like sleepwalking or hypnosis) that put the issue into contention. When we think about insanity law going forward, I recommend that we allow the law of insanity to fork and develop along two paths. One path would carry forward the common law tradition of excusing the morally blameless by retaining the right-and-wrong test. The other path would be a path of experimentation and a vehicle for bringing new medical insight about mental health into the courtroom. This approach acknowledges that the common law’s traditional concern to criminalize only the morally blameworthy is older than and distinct from modern psychology and psychiatry. We can retain our commitment to this normative tradition, while acknowledging that advances in the scientific understanding of the mind will warrant new doctrinal vehicles for presenting mental health evidence in the courtroom.