You may believe that whether a person is found not guilty due to insanity depends on the courts, on the doctors, or even just on the money they paid their lawyer. It doesn't. It depends on what you think of insanity as a legal defense.

We contacted Professor Stephen J .Morse, a Professor of Law and of Psychology and Law in Psychiatry at the University of Pennsylvania, to give us some idea of how the insanity defense works in the real world. Morse is both a lawyer and a psychologist, though he states that the insanity defense is not a medical issue. He believes that legal insanity is "entirely a legal issue," and when we examine at the most famous case involving it, it looks like he's right.

The Unavoidable Daniel M'Naghten

Any discussion of insanity as a legal defense will circle back to Daniel M'Naghten. In 1843, M'Naghten was a troubled man who believed that his troubles were caused by the Tory party. They were persecuting him, were going to kill him, and had "entirely destroyed [his] peace of mind." After some thought, he decided to remedy this by shooting Robert Peel, the Tory Prime Minister. M'Naghten took a shot at Peel's carriage and killed its occupant, although its occupant was Edward Drummond, Peel's private secretary.

Advertisement

During the trial, the defense argued that M'Naghten was suffering from delusions of persecution. The prosecution argued that he was sane enough. While the prosecution called non-experts like M'Naghten's landlady to testify that he seemed perfectly normal day-to-day, the defense produced medical experts who declared M'Naghten insane. The jury decided that since only the defense had produced medical experts, M'Naghten was not guilty by reason of insanity. Daniel M'Naghten spent the next two and a half decades of his life in asylums, but he never accepted that he had been delusional.

This was not what led to the modern standard of legal insanity.

What led to the modern standard was the furor after the verdict. The Tories were also not pleased that the person who had taken a shot at their leader was found not guilty. The controversy about M'Naghten was so heated the House of Lords revived a rarely exercised right to question judges, and asked the peers known as Law Lords designed to pin down the conditions under which defendants were no longer legally responsible for their crimes. The judges' answers defined the defense. The most important passage describes the insanity defense like this:

Advertisement

"To establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused as labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong."

The Lords did ask questions about the circumstances under which medical experts might be qualified to judge a person's level of sanity, but doctors didn't determine the meaning of insanity as a defense. The actual meaning of what it means to be legally insane — a meaning that still has significance today — was worked out by a group of judges in response to a group of politicians.

Beyond The M'Naghten Rules

But the insanity defense, Professor Morse says, did not start with the M'Naghten case. A century before that, those who had committed crimes were subjected to the much more colorfully named "Wild Beast Test." Any person whose mental state left them "akin to a wild beast" could not be held responsible for their crimes. And it goes farther back than that. As long as there has been a system of law, there has been a recognition that someone who is unable to understand the nature of their acts cannot be punished for them. Although they might be separated from society for the safety of others, their sentence has to be just that – separation, not punishment.

This history is important, because the insanity defense did not end with the M'Naghten case, either. Over the last few decades, some states have changed their definition of insanity and some have gotten rid of insanity as a legal defense. Like anything to do with the insanity defense, this was a controversial move and has led to some prolonged legal battles. Among those battles is the case of John Delling, a young man in Idaho who killed two men because he believed they were shrinking his brain and stealing his soul. Idaho does not allow for an insanity defense. Facing the death penalty, Delling pleaded to second-degree murder and was sentenced to two concurrent life sentences. When Delling and his lawyers appealed to the Supreme Court, Morse submitted an amicus brief, stating that the lack of availability of the insanity defense was not just wrong but unconstitutional.

Advertisement

The long history of the insanity defense was one of the reasons Morse gave as to why denial of the insanity defense is unconstitutional. Shielding from punishment those who are unable to understand their crimes is one of the oldest traditions of western law. It's one of the law's better traditions. Even when we were hanging petty thieves we were able to recognize that it was wrong to hold people morally accountable if they were not "morally responsible agents," as Morse describes them. He believes that abolishing the insanity defense will always be wrong "unless you can come up with another set of doctrines that can do the same justice as the insanity defense." Idaho, he argues, had no such doctrines in place.

In 2012, the Supreme Court declined to hear the appeal.

But Really, What Is Insanity?

The M'Naghten definition of the insanity defense is still preeminent, but there have been a few tweaks. One early innovation is the control test. Also known as the volition test, it allows a criminal to use insanity as a defense if they knew what they were doing was wrong, but felt an irresistible impulse, an urge beyond their control, to commit the crime anyway. Professor Morse doesn't like them. Why? "Because we don't understand them and can't apply them fairly."

He believes that the M'Naghten test pretty much covers any situation in which insanity as a defense should be applicable, but this is where we run into problems. The shorthand for the rule states a criminal is not guilty if he unable to understand that what he is doing is wrong. By some interpretations, M'Naghten was not insane at all. He was operating under a mistaken assumption – that the Tories were out to get him – but he knew what would happen when he fired a gun at a person and he knew that what he was doing would be considered against the law. A more modern and heartrending example is Andrea Yates, the woman who drowned her five children in her bathtub. Yates knew what she was doing was wrong in the eyes of any other member of her community, and she knew what she was doing was illegal. But she was convinced that if she didn't kill her children immediately, she would corrupt them to the point that they would go to hell. By drowning them, she believed that she was saving them from torture.

Advertisement

So should Daniel M'Naghten or Andrea Yates be considered sane because they were able to understand the law and the prevailing moral codes of their community? Or should they be considered insane because they were unable to recognize the reality of the situation? There is room to interpret the legal guidelines, and that interpretation makes a huge difference to defendants.

Different states have slightly different takes on what constitutes legal insanity, but Morse says that the wording of the test itself doesn't really make a difference. States have tightened up and loosened their definitions of insanity as a defense, and it hasn't affected how people interpret the concept. I ask him if perhaps the insanity defense is more likely to be successful with defendants who inspire sympathy. So would a mother who kills the postman because she believes he's an alien planning to murder her kids be more readily accepted as insane than a convicted felon who kills the teenager across the street because the he thinks the kid is a CIA agent out to execute him? Morse disagrees that sympathetic victims can use the defense more successfully.

Right now, he says, "unless the defendant is psychotic," there's very little chance an insanity plea will be successful. Even if the defendant is psychotic it often won't work, he believes. What makes a difference isn't wording of the laws or how sweet and understandable the defendant is, it's the attitude of society. The public decides how they want to treat people who commit crimes but are mentally, for lack of a better word, off. Our attitude determines how far removed from reality they have to be before they are no longer responsible for what they do. That attitude changes as society changes, according to Morse. "Sometimes it's feeling tougher and sometimes it's feeling more tender," he says. What we think about insanity, and how much tenderness we think is appropriate, will determine the fate of any person on trial.

Advertisement

Note: I'd like to thank Professor Morse for being very generous with his time and expertise.

[Via Daniel M'Naghten's Case, Knowing Right From Wrong, Supreme Court declines to review insanity defense appeal.]

Top Image: Library of Congress Prints and Photographs, Supreme Court Image: Matt H Wade, Judges Robes Image: International Court of Justice.