Could Neuroscience Exonerate Showtime Serial Killer Dexter Morgan?

A 1950s electric chair

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On Monday, Oct. 22, Future Tense—a partnership of Arizona State University, the New America Foundation, and Slate—will host “My Brain Made Me Do It,” an event examining how neuroscience is affecting the legal system, in Washington, D.C. For more information and to RSVP, visit the New America Foundation website.

It is the moment every Dexter lover fears: Our green-eyed antihero comes home after a tiring day at the blood spatter lab. Tonight he’ll stalk his latest victim, a psychopath who keeps eluding his buddies at Miami Metro homicide, but for now it’s time to hang out with his son, Harrison. Except the air suddenly fills with flashing lights and the wail of sirens. A SWAT team bursts in and wrestles Dexter to the ground. “Dexter Morgan,” says the lieutenant (please let it not be Deb), “You are under arrest for 120 counts of first degree murder.”

Even typing this imaginary scene makes my throat tighten. But let’s say the law somehow—horribly, unthinkably—caught up with Dexter after seven seasons of definitely disturbing but arguably righteous- and-also-look-at-his-cheekbones-no-really-look-at-them murder. What would happen then?

We should start by thumbing through the accused’s profile. Dexter Morgan is a serial killer who experiences powerful urges to butcher people. He developed these drives after a heinous childhood trauma left him soaking for days in the blood of his murdered mother. A police officer working the crime scene, Harry Morgan, discovered the young Dexter and adopted him, but recognizing that the child would forever carry a burden of darkness, devised a code to regulate its expression. Harry’s Code says, essentially, that if you must kill someone, you should kill another murderer. It also contains guidelines for verifying a target’s guilt and escaping detection. The end result of this highly unconventional parenting is that the bloody-minded Dexter serves as Miami’s own avenging angel.

Should the legal system get its hooks into Dexter, though, he’d be in serious trouble. His best bet, says Richard L. Jacobson, a counsel at the Arnold & Porter law firm, would be to plead insanity. Most “enlightened” jurisdictions (New York, Massachusetts, California, etc) define a mental defect that compels you to break the law as madness. If Dexter’s attorneys could demonstrate that he had no power to rein in his urges, they might be able to secure him a permanent room in an asylum instead of a cell on death row. Of course, not all districts are so lenient—the meaning of legal insanity slipslides as you move across state lines. In Florida, for instance, where Dexter would likely stand trial, reprieve exists for the “cognitively insane,” but not the “volitionally insane.” In other words, if you are too deranged to understand what you are doing or its consequences, or to perceive that your actions are wrong, you can plead madness. But if, like Dexter, you apprehend the difference between right and wrong and knowingly commit a crime, no dice. You’re guilty whether or not you can resist your pathological impulses.  

U.S. courts once used a test called the M’Naghten Rule  to determine criminal insanity. The test takes its name from Daniel M’Naghten, an Englishman who suffered a psychotic episode in 1843 and shot the secretary to the prime minister. (He was aiming for the PM, whom he believed wanted to kill him.) The rule makes the insanity defense available only to those intellectually unable to tell the difference between right and wrong. In 1929, the United States modified the M’Naghten Rule with an “irresistible impulse” test, allowing courts to acquit defendants who seemed too enthralled by crazy urges to control their behavior. And then, in 1954, Judge David Bazelon of the U.S. Court of Appeals for D.C. loosened the weave of the legal net still further. His decision in the groundbreaking Durham v. United States case simply holds that “an accused is not criminally responsible if his unlawful act was the product of mental disease.”

But judges found the Durham Rule too permissive. In addition to absolving those suffering from hallucinations or psychosis, it provided an easy out for alcoholics, drug addicts, and compulsive gamblers. In 1972, the Brawner v. United States verdict offered a return to a definition of insanity that was only slightly slacker than the one outlined by the M’Naghten Rule. Today, different states maintain their own tests of madness. Dexter would be lucky to end up in a place that saw his “dark passenger” as mind-clouding affliction, not pure evil.

So what if—as seems likely—the insanity defense failed? Let’s face it: Dexter did commit a lot of homicide. Assuming the state had gathered enough admissible evidence, he would be handed a guilty verdict. His lawyers would then turn to softening his sentence any way they could. And they’d have work to do: In places like Florida, Texas, Mississippi or Alabama, it’s safe to assume the prosecution would push for the death penalty.

Would the fact that Dexter only kills murderers make any difference? “If I were defending Dexter,” says Jacobson, “I might try to introduce evidence that the people he killed deserved to die. I’d hope to get the jury to acknowledge that he was performing a public service.” But, he adds, chances are the prosecution would succeed in excluding whatever details he furnished on grounds of relevance. “It would be inappropriate for the jury to pass judgment on whether these guys would have been found guilty had they received due process,” he says. “Our system of law is predicated on the idea that you are innocent until proven otherwise by a jury of your peers.” Anyway, Dexter frequently murders baddies who for whatever reason lie beyond the reach of the American justice machine. Tried in court, the majority of them would likely be declared not guilty and that would look even worse for Dexter.

At this point, images of my droll Sunday night heartthrob at the mercy of the law made me want to curl up in a fetal position and keen. But over time, developments in neuroscience could—could­—transform the judicial system into a friendlier place for Dex. Courts are beginning to contend with fMRI evidence that might call free will into question. They are wondering whether some people are forced by brain abnormalities into the back alleys of crime, whether there are “born felons,” whether “neuroscience made me do it” could ever fly as an defense. And while substantial changes to the legal process seem a long way off, perhaps Dexter can keep his cat-and-mouse game going until everyone knows a bit more about how the brains of people like him work. Perhaps he can still win over the hard-hearted with his meltingly soft gaze and, um, profusion of early biological risk factors.  

Or maybe, next time he kills someone, he should just be extra careful to wipe off his fingerprints.