The ‘West Memphis Three’ and combating cognitive biases

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Last week, the “West Memphis Three” were released from prison, having spent half their lives — 18 years — behind bars for crimes they almost certainly didn’t commit. So what made prosecutors and investigators sure they had the right guys, and why were those beliefs, once established, so hard to reverse?

The crimes for which the three Memphis men were convicted were brutal. Three 8-year-old Cub Scouts were found dead, hogtied and apparently mutilated. The police decided early on that it was likely the boys had been victims of a satanic cult killing, which led them to consider self-described Wiccan teen Damien Echols, a young man with asymmetric black hair, a pale face and oddball taste in clothes and music. They hauled in an acquaintance of his, a minor named Jessie Misskelley, who had an IQ of 72, and interviewed him for hours without his parents or an attorney present. Finally, he confessed, implicating Echols and another friend, Jason Baldwin.

The confession confirmed what police expected to hear — that Echols was involved — which may be why they accepted it at face value. But Misskelley’s account contradicted the evidence in multiple ways. The time he initially gave for the murders was noon, an hour for which the other teens had an ironclad alibi (they were in school); he said that the other suspects raped the boys, but the medical evidence showed no physical trauma consistent with rape and no semen was found in any body cavity; he said the boys were tied up with a brown rope, when they were actually found tied with their own shoestrings.


An overarching problem, which this case illustrates perfectly, is that humans have a tendency to see what they expect to see. Much psychological research shows that people are subject to an array of “cognitive biases” that affect their evaluation of evidence, and prosecutors and sworn officers are by no means immune to the phenomenon.

Investigators and prosecutors, even when they are trying their best to do their jobs, may seek out or take special notice of evidence that confirms their prior beliefs rather than evidence that challenges it. And they are likely to interpret ambiguous evidence in ways that accord with their preconceptions.

Misskelley promptly recanted his confession. But prosecutors nonetheless pressed the case, and he and the others were ultimately convicted. The prosecutor’s case was based largely on character assassination, innuendo and the not-very-credible testimony of the likes of a jailhouse snitch and a witness with a mail-order doctorate. Not a shred of physical evidence linked any of the young men to the crime scene (and post-conviction DNA testing has also failed to find any biological evidence that they were there). Echols received the death penalty, the others life sentences.


That’s how things might have ended if two documentary filmmakers hadn’t ventured to Arkansas to make a film about the case. Initially they thought they would be examining a sensational satanic cult killing. But the more research they did, the more they began to doubt that it was a cult killing and that the men who were convicted were the perpetrators. Their film suggested the defendants had been railroaded, and it led to widespread publicity and higher-powered legal representation.

But nothing happened quickly. The film came out almost 15 years ago. Even now, to win freedom, the three men agreed to Alford pleas, whereby they proclaimed their innocence but formally pleaded guilty nonetheless.

The case demonstrates the need for criminal justice and evidentiary reforms that would make wrongful convictions less common on the front end. Although releasing some fraction of those wrongfully convicted afterward is all to the good, it would be even better if there were fewer of them in the first place.


So what produces wrongful convictions? At least three of the often-seen causes were present here: dubious forensic science evidence, false confessions and evidence from unreliable jailhouse informants who often have a strong incentive to tell law enforcers what they want to hear.

Cognitive bias helps explain why prosecutors can focus on a suspect (or three) and fail to see the warning signs that they are headed down the wrong path. Cognitive bias is not the same thing as racial bias or personal animus. It’s the habit of our brains to let the first fact we encounter guide our evaluation of the second and the third. One false start can lead to a miscarriage of justice more quickly than any of us would like to believe.

In this case, once the cops saw Echols as something of a freak, an odd duck who read about witchcraft, liked Metallica and didn’t exactly fit in, the jump from weirdo to likely satanic cult killer was easier than it should have been. Facts that didn’t really prove anything were lumped together with suspicions and dubious theories.

We can’t eliminate cognitive biases altogether; they’re part of how we think. But we can design procedures to reduce their effects on investigators, prosecutors and even jurors. Police departments and prosecutors can and should implement mechanisms explicitly designed to combat it. For example, in every major case, an investigator or prosecutor with no prior involvement could be asked to review the evidence and assess its strengths and weaknesses. Even better would be if this reviewer weren’t expected to provide a “neutral” review but instead were assigned the role of devil’s advocate, explicitly asked to find the flaws in the prosecutors’ theory. In this case, the filmmakers played an equivalent role, but most defendants aren’t so lucky.

If this high-profile release helps spur thoughtful attention to the problems of combating cognitive bias in police departments and prosecutors’ offices, then some good could still come out of a terrible wrong. Bad convictions harm everyone. Not only do they put innocent people behind bars; they also leave actual criminals — in this case a child murderer — on the streets.

Jennifer L. Mnookin is a professor at UCLA Law School.