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Volokh Conspiracy

Can States Eliminate the Insanity Defense?

A fascinating and important criminal law case to be argued next week on the first day of the new Supreme Court Term.


The Supreme Court's new Term will begin next week with a fascinating criminal law case, Kahler v. Kansas, that asks a simple question: Can a state eliminate the insanity defense?  I think Kahler may prove quite important for the field of criminal law, and I wanted to explain why.

Let me start at the beginning.  Specifically, let's start in the first week of 1L year, when most law students are introduced to criminal law.  Crimes, they learn, must include an actus reus—a guilty act.  Crimes must also include mens rea—a guilty mind.  For a crime to occur, the actus reus and mens rea must happen concurrently.  That's been the traditional law of crimes going back to the common law hundreds of years ago.

Around the same time that 1Ls are learning this, they are also learning the modern arrangement that crimes are enacted by legislatures rather than courts.  What is a crime is now up to legislatures, not judges.  And this creates a problem.  The traditional requirements of actus reus and mens rea are common law rules.  Courts announced them hundreds of years ago in a time when courts largely defined what was a crime.  When courts define what is a crime, the courts were saying, they will define them in ways that include a guilty act and guilty mind requirement.

But in the modern world, in which legislatures define what is a crime, the common law rules for what is a crime are no longer obviously binding.  What matters today is the constitutional limits of crime definitions.  In a modern system, legislatures can legislate in the zone of whatever the constitution allows.  So that naturally raises a question: What are the constitutional limits of crime definition?

There is surprisingly little law answering that question.  There is some, but not that much.  That's surprising, I think, because the constitutional limits on crime definition are fundamentally important.  But there's also a reason for the relative absence of caselaw.  Legislatures enact lots of new crimes, but they usually use preexisting tools to get there. And when legislatures enact criminal laws that may on their face seem like significant departures from traditional approaches, courts construe the new laws to reflect traditional common law principles.

That brings us to the new case, Kahler v. Kansas.  The state of Kansas has effectively eliminated the insanity defense.  "Mental disease or defect is a defense to a prosecution under any statute," Kansas law says, only if it negates "the mental state require[ment] as an element of the offense charged." Kan. Stat. Ann. § 22-3220 (2009).  In other words, a defendant is always free to show that his insanity explains his innocence of the crime charged.  But that's the only way insanity can be used. It's not an independent defense.

Here's a hypothetical to see the difference.  Imagine a person suffering from mental illness pushes a victim off a bridge.  The victim falls to his death.  The pusher is then charged with intentionally killing another human being.  At trial, the defendant cannot argue to the jury that he is not guilty by reason of insanity because his mental illness impaired his ability to identify right from wrong or to conform his conduct to the law.  For example, he can't argue that he heard voices telling him to kill the victim that he couldn't ignore.

Instead, the defendant can only argue to the jury that his mental illness is the explanation for why he lacked the intent to kill and is therefore not guilty of an intentional killing.   For example, he could argue that his mental disease meant that he wrongly believed his victim could fly: Because he didn't realize that pushing the victim off the bridge could harm him, he didn't cause the victim's death intentionally.

The facts of Kahler are stark, even though they don't technically matter much to the legal question.  The defendant murdered his estranged wife, his two daughters, and his wife's grandmother.  At trial, he was not permitted to put on evidence that, as a result of mental disease or defect, he was unable to recognize the wrongfulness of his acts or conform his conduct to the law.  He argues that Kansas's repeal of the traditional insanity defense violates both the Due Process clause and the Eighth Amendment's ban on cruel and unusual punishment.

What's interesting to me about the briefing in the case is how much is up for grabs.  You can think of different ways the Court might approach the question.  Consider these four:

(a) Deviation from the Common Law. You might ask if Kansas's effective elimination of the insanity defense is a sharp deviation from common law approaches.

(b) Deviation from Framing Era Understandings.  You might ask if Kansas's approach would have been considered out of bounds under the original public meaning of the Constitution, either at the time of the ratification of the Eighth Amendment (in 1791) or of the Fourteenth Amendment (in 1868).

(c) Deviation from Current Practices.  You might ask if Kansas's approach is a sharp outlier from prevailing trends in state law approaches to the insanity defense.

(d) Deviation from Criminal Law Theory.  You might ask if Kansas's approach is inconsistent with the retributive and deterrent theories of punishment that today are understood to justify punishment and impose limits on the scope of punishment.

Under any of these approaches, or combination of approaches, you then need a theory of how far a deviation from those standards is permitted.  The Court could be pretty deferential, allowing deviations as long as they are not particularly large (which might avoid the need for lots of judicial line-drawing but also limit the Court's role).  Or the Court could be more strict, allowing only small deviations (which would ensure a significant role for the Court but could also require difficult judicial line-drawing).

And whatever approach the Court applies here, its approach presumably will shed light on what other crime and defense definitions are constitutionally required.  Kahler might be a case 1Ls learn not just when they cover the insanity defense but also when they learn about the constitutional limits of crime definition more generally.

The case will be argued next Monday, October 7th, on the first day of the new Supreme Court term.  As always, stay tuned.