The New Insanity Defense Standard

Release time: 2020-04-09 09:30

The New Insanity Defense Standard

Is moral culpability required for conviction?

The Supreme Court has ruled: the state of Kansas can drop moral capacity as a requirement for criminal conviction. In most states, those who do not comprehend the rightness or wrongness of their actions are insane rather than criminal, but not in Kansas.

Splitting M’Naghten

Justice Elena Kagan, who usually sides with the liberal justices, wrote the opinion in Kahler v. Kansas for the 6-3 majority (including the five conservatives: Alito, Gorsuch, Kavanaugh, Roberts, and Thomas). Three liberal justices dissented (Breyer, Ginsburg, and Sotomayor).

The new standard described by Kagan explains the venerable M’Naghten rule from 1843 as comprising two distinct prongs. The first is cognitive capacity: An individual who does not comprehend the consequence of what he is doing is insane. The second prong is moral capacity: an individual who does not comprehend the rightness or wrongness of their action is also insane.

Kansas agrees that the first prong (lack of intent) establishes insanity, but insists that the second (lack of moral understanding) does not. So in Kansas, a person who fully intends to kill someone, but is morally disabled to the point that they don’t know it is wrong (for example, by the delusion that the victim will be reborn immediately in a better state) can be convicted of murder. In most states, the same person would not be legally responsible.

There are other, less stringent standards for establishing criminal insanity (including volitional control or substantial contribution of mental illness), but the question here is what is the most stringent standard a state can impose without violating the U.S. Constitution? Does a state have to provide the moral capacity prong of M’Naghten?

Our highest court has said no. A state is free to judge a person who cannot distinguish the morality of their actions to be sane and criminally culpable.

In this particular case, James Kahler killed his ex-wife, two daughters, and his mother-in-law. He was convicted and sentenced to death, but he was denied the opportunity to present evidence that his mental illness blocked him from understanding the wrongness of the violent actions he fully intended to commit. Those facts are undisputed. But the way Kansas understands the facts about insanity is another story.

Disagreement on the Facts of Mental Illness

The dissenters (led by Justice Stephen Breyer) say that the court’s ruling is constitutionally wrong because it is empirically wrong.

According to the three dissenters, the M’Naghten rule embodies a fundamental principle grounded in reality as well as morality: “Its basic insight is that mental illness may so impair a person’s mental capacities as to render him no more responsible for his actions than a young child or a wild animal. Such a person is not properly the subject of the criminal law” (3). Breyer seems sure that this is true and cannot be disputed by reasonable people.

The court disagrees. In the view of six of the justices, the empirical reality is not clear. The facts are disputable and disputed because the “uncertainties about the human mind loom large.” (8) Therefore Kansas can decide for itself.

The American Psychiatric Association (APA) filed a brief arguing against the court’s position, agreeing with Breyer that the facts of insanity are much better known. The APA expresses confidence in the ability of the profession to recognize insanity, asserting that “the professional experience of mental health professionals demonstrates the benefits of the insanity defense.” (32)

The crux of Breyer’s disagreement with the court comes near the end of the dissent: “Kansas’ abolition of the second part of the M’Naghten test requires conviction of a broad swath of defendants who are obviously insane.” (21) The key word is obvious. This form of insanity is obvious to Breyer, but not to Kagan, nor to the legislators of Kansas.


The court frames the question in a clear way: Have we come to a point that we know—in which we are in consensus about what is true and false—about insanity and its borders? The psychiatrists and three justices suggest the answer is yes, while the legislature of Kansas and the court’s majority of justices say the answer is no.

The Federalism of Facts

Federalism is the long-standing constitutional principle that individual states have the power to determine many of the laws and regulations within their own borders. For example, federalism explains why criminal penalties and voting procedures are somewhat different from state to state. The diversity of laws is long-standing and well-established, but the diversity of facts is a newer proposition.

Can one state, or a small group of states, declare that a fact recognized by most of the nation is different within their borders? The Kahler decision seems to be a large step in that direction.

The bounds of factual federalism drawn by Kagan seem to hinge on how disputable a perceived reality is. Do we know versus merely hold legitimate conflicting opinions that are open to dispute? In the case of insanity, “across both time and place, doctors and scientists have held many competing ideas about mental illness.” (23) If it were a matter of settled expertise, that would be one thing. But since it is not, it must be decided by democracy rather than science.

The court concludes that defining insanity and the insanity defense “is a project, if any is, that should be open to revision over time, as new medical knowledge emerges and as legal and moral norms evolve. Which is to say that it is a project for state governance, not constitutional law.” (24)

How far the federalism of facts extends—to which realities at what times—is unclear, but at the very least the current court believes it applies to the nature of insanity.


David C. Barker, Ph.D., is Professor of Government and Director of the Center for Congressional and Presidential Studies (CCPS) at American University.


Morgan Marietta, Ph.D., is Associate Professor of Political Science at the University of Massachusetts Lowell, where he studies and writes about the political consequences of belief.

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