Artist rendering of a judge presiding over a hearing in 2003 for John Hinckley Jr., the man who tried to kill President Reagan in 1981 and was found not guilty by reason of insanity, second from right. Public outrage following the trial led to law changes that narrowed the grounds for a verdict of insanity.Dana Verkouteren / AP

Historians are not quite sure whether Daniel M’Naghten, a Scottish woodworker, intended to kill Edward Drummond or Drummond’s boss, the English prime minister Robert Peel. In fact, he killed Drummond. What is more certain is that he did not intend to bedevil generations of law students and judges, but he has. His ghost will be present in the Supreme Court chamber this Monday, when the Court opens its October 2019 term.

The issue will be whether Kansas and four other American states—Alaska, Idaho, Montana, and Utah—can essentially abolish the “insanity defense,” the test for which bears M’Naghten’s name.

Born in 1813, M’Naghten by 1841 had begun to believe that members of England’s Conservative Party were persecuting him. In 1843—perhaps believing he was shooting the prime minister—M’Naghten shot Drummond, a civil servant, from behind at point-blank range. Drummond died five days later.

At trial in the Old Bailey, medical witnesses testified that M’Naghten’s delusions had left him unable to understand or control his actions. The evidence was so strong that the prosecutor concluded, “I cannot press for a verdict against the prisoner.” The jury found him not guilty by reason of insanity; he died about 20 years later in Broadmoor Asylum.

After the verdict, the House of Lords asked the judges of the Court of Common Pleas to explain the proper legal test for insanity. Their answer was, “That before a plea of insanity should be allowed, undoubted evidence should be adduced that the accused was of diseased mind, and that at the time he committed the act he was not conscious of right and wrong.” The test has over time come to be formulated as something like this (from Black’s Law Dictionary): “A person is not criminally responsible for an act when a mental disability prevented the person from knowing either (1) the nature and quality of the act or (2) whether the act was right or wrong.”

Legal insanity is what’s called an “affirmative defense,” meaning that the defendant, not the prosecution, must prove it. That’s usually done with a psychiatrist testifying that a defendant suffers from an identified mental illness that renders him or her incapable of understanding his or her actions. If a jury (or a bench-trial judge) buys the defense, the accused will be committed to a mental institution until a medical panel decides he or she is no longer a danger to society.

Though it’s called the M’Naghten rule, the standard in most states today encapsulates centuries of legal evolution. New factors have been added on, such as a requirement of an “irresistible impulse,” but the not knowing “right and wrong” test remained central to legal insanity in most states.

But five have moved away from that standard, and that story begins on March 30, 1981, when 25-year-old John W. Hinckley Jr. fired shots at President Ronald Reagan as Reagan was leaving a speech at the Washington Hilton. His bullets wounded two Secret Service agents and permanently disabled the presidential press secretary James Brady; one bullet pierced Reagan’s chest. Doctors at George Washington University Hospital saved his life.

At trial, Hinckley’s lawyers revealed that their client had been obsessed with delusions about the actress Jodie Foster, and decided to kill a president as a way to impress her. The jury found him not guilty by reason of insanity; he was committed to St. Elizabeths Hospital in Washington, D.C. (He was finally released only in 2016, on the condition that he live with his mother.) Public outrage led to changes in many state and federal laws, narrowing the grounds for a verdict of insanity. The most extreme change—passed in some form by five states—eliminated the affirmative defense altogether. Instead, it provided that a defendant could challenge the evidence prosecutors use to prove that the crime was committed with the required “mens rea,” meaning “mental state”—which, in the case of murder, means that the defendant intended to kill a human being. The “right and wrong” test was eliminated.

Justice Stephen Breyer, like the former law professor he is, in 2012 explained what that change means:

Case One: The defendant, due to insanity, believes that the victim is a wolf. He shoots and kills the victim. Case Two: The defendant, due to insanity, believes that a wolf, a supernatural figure, has ordered him to kill the victim. In Case One, the defendant does not know he has killed a human being, and his insanity negates a mental element necessary to commit the crime. In Case Two, the defendant has intentionally killed a victim whom he knows is a human being; he possesses the necessary mens rea. In both cases the defendant is unable, due to insanity, to appreciate the true quality of his act, and therefore unable to perceive that it is wrong. But … the defendant in Case One could defend the charge by arguing that he lacked the mens rea, whereas the defendant in Case Two would not be able to raise a defense based on his mental illness.

This brings us to the case of James Kraig Kahler now before the Court. Kahler has been diagnosed with “mixed obsessive-compulsive, narcissistic, and histrionic personality” (to quote his lawyer’s brief). For years he was able to hold a job and form a family—a wife, Karen, and three children. In 2008, however, the family moved from Texas to Columbia, Missouri, where Kahler became the director of Columbia’s Water and Light. Karen, meanwhile, began an affair with a woman. Kahler had given permission for the affair, but he now entered a major depression. His mood and actions deteriorated—he was obsessed with jealousy, and badgered his daughters with tales of his wife’s betrayals. The marriage broke up and he lost his job. During the Thanksgiving 2009 holiday, he drove to the home of Karen’s grandmother, Dorothy Wight, where the rest of the family was celebrating. There he deliberately hunted down and killed Karen, Dorothy, and two of the children, allowing only his son to escape.

At trial, he offered psychiatric testimony that his condition had become “severely degraded so that he couldn’t refrain from doing what he did.” The state offered its own expert, who testified that Kahler was mentally ill but was fully capable of forming the intention to kill. The defense asked the judge to instruct the jury to consider insanity as an affirmative defense; the judge refused because the Kansas statute did not allow it. Instead, defense lawyers argued to the jury that Kahler was so impaired that he could not form the intent; the prosecution, pointing to his methodical actions, argued he could. The jury found him guilty and sentenced him to death. After losing on appeal, the defense petitioned the Supreme Court, presenting the question, “Do the Eighth and Fourteenth Amendments permit a state to abolish the insanity defense?”

The Court hasn’t considered the issue before. In 2012, it refused to decide the issue in a case called Delling v. Idaho. Breyer dissented from the denial of review; in his dissent he offered the summary I quoted above. Six years earlier, the Court had decided Clark v. Arizona, a case concerning a statute that is a weird mirror image of the Kansas law: Arizona did not permit defendants to present expert psychiatric testimony to prove they lacked the mens rea (which Kansas, by contrast, does allow) but did allow defendants to prove they could not tell right from wrong (which Kansas does not allow). The Clark majority noted that “insanity” in a legal sense has no real psychiatric meaning, and that states disagree on how to embody the concept in law. “There being such fodder for reasonable debate about what the cognate legal and medical tests should be, due process imposes no single canonical formulation of legal insanity,” Justice David H. Souter wrote for five justices.

Kahler’s brief suggests that M’Naghten was not a newfangled Victorian notion, but rather a codification of common-law principles that go back to medieval English law. If that is so, it is easy to conclude that it must be a part of “due process of law.” The American Psychiatric Association, in an amicus brief, cites scientific evidence that the inability to tell right from wrong is not a lawyers’ fabrication but a recognized effect of some forms of mental illness; while most of the mentally ill are harmless, a small number become so deluded they do not know right from wrong. Punishing those who don’t understand what they did, the APA brief suggests, does not serve the moral function of criminal law, and by definition cannot deter people who later fall under similar delusions.

Kansas in its brief emphasizes the federalism argument: “This Court has repeatedly held that the Due Process Clause leaves states with substantial flexibility to determine the substance of their criminal law, and this flexibility is at its zenith when it comes to the question of insanity.” Kansas further suggests that, because the definition of insanity has been stated in different ways, M’Naghten is not deeply rooted in the history of the law and thus not an inescapable aspect of due process.

Kahler’s brief calls the Kansas statute “a misinformed reaction to a pair of headline-grabbing cases.” That seems like a false step. A Court that saw nothing amiss in Donald Trump’s anti-Muslim rhetoric may not be eager to judge the mens rea of 1980s legislators. But if it is a mistake, it is that of uttering in court what everyone knows to be true: In the rush to foreclose future Hinckleys, legislatures had little concern for the real facts of mental illness.

Lincoln Caplan covered the Hinckley case for The New Yorker and later wrote a book, The Insanity Defense and the Trial of John W. Hinckley, Jr. (Caplan is a college friend, and his book was part of what inspired me to go to law school.) “It’s absolutely the case that the Hinckley verdict and its impact on law reform is a case study of panic and of ignoring the evidence,” he told me in an interview. The changes in the law of insanity were part of, he went on, “a massive retributive reform of criminal justice that began in 1980. The Reagan administration misrepresented the insanity defense as supposed proof of lawlessness in American society and as a supposed symbol of what was going on in criminal justice. It had the force that that kind of demagogy needed—which was instilling fear.”

In the larger sense, Kansas’s statute and others like it are relics of that time of hasty political grandstanding by both parties, the era that brought the nation mandatory minimums and mass incarceration. Kahler’s hope is that the Court is feeling the social hangover that much of the country feels.

This story is part of the project “The Battle for the Constitution,” in partnership with the National Constitution Center.

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