Why Serial Killers Are Disturbingly Good At Passing Lie Detector Tests

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At this point, we all know that lie detectors don’t actually detect lies, right? They’re so unreliable, in fact, that polygraph results aren’t allowed in courts as evidence. They measure the physiological responses of an interviewee as an interviewer asks questions, like heart rate, blood pressure, respiration, galvanic skin response (changes in skin conductivity), etc. There’ll be some baseline questions like, “Is your name [blank]?,” and then questions meant to provoke a physiological response. The belief is this: If someone is freaking out about being caught in a lie, their vital signs will show it (here’s what really happens to your body when you take a polygraph test). But there’s the problem: If someone doesn’t feel certain emotional responses, then the machine isn’t going to detect anything. 

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This is why serial killers are reportedly — reportedly, we stress — so good as passing polygraphs. Retired FBI agent John Douglas, author of “Mindhunter: Inside the FBI’s Elite Serial Crime Unit” (the book that the”Mindhunter” show was based on), said as much. “Many serial killers like Ted Bundy and the Green River Killer have passed polygraph tests over and over again,” he said in his Masterclass, adding that they don’t experience the anxiety that the average person would. “Their heart doesn’t race, you know, like yours would.” 

All in all, Douglas dismisses polygraphs because there’s no way to determine how a person might respond to being questioned in a high-pressure situation. In fact, polygraphs have about a 50% chance of producing a false positive, meaning that they say a person is lying when they’re not. And in the case of serial killers, who may or may not demonstrate psychopathic traits, polygraphs may be fairly useless.

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“Psychopath” is a word that gets tossed around quite a lot. “What a psychopath!” or “He’s a complete psycho,” we’ve all heard someone say — or said ourselves. While many take “psychopathic” to mean something like “manipulative,” “uncaring,” “unhinged,” etc., this general idea omits psychopathic attributes like a lack of empathy, remorse, and even feelings in general. Online interviews with self-described psychopaths like Lewis Raymond Taylor on People Are Deep attest to this fact. He straight-up says that he doesn’t know what remorse feels like.

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So, how would a person like Taylor fare on a polygraph test designed to check physiological responses related to emotions like anxiety? And to go many steps further, what about a serial killer like Ted Bundy? Bundy received a score of 39 on the Hare Psychopathy Checklist, a longstanding psychological inventory of 22 items that checks for psychopathic traits. That’s one shy of the highest score possible of 40. And while there’s some disagreement on whether or not Bundy actually ever actually took a polygraph, another serial killer, Gary Ridgway, did and passed.

At the same time, it’s important to note that not all serial killers are psychopaths, because “psychopathy” isn’t a disorder. “Psychopath” is an informal, loose term describing a set of personality traits related to disorders like antisocial personality disorder (APD) and borderline personality disorder (BPD). So is it possible that a serial killer would not have one of these diagnoses? Yes. Is it possible that a serial killer might not psychologically qualify as a psychopath? Yes. But can a serial killer sidestep a polygraph regardless? Yes.

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Ultimately, we can’t ever know 100% why a serial killer is good at passing a lie detector test, if that’s even the case. As mentioned, individuals like retired FBI agent John Douglas assert that it’s because of a lack of anxiety and “because they [serial killers] feel like the crimes are justified.” But that’s just a deduction. Given the unreliability of lie detector tests, their long-debunked status as a real tool of criminal justice, their tendency to produce false positives, and the disconnect between assumed methods of emotional response and individual variation in those responses, well … we can only say for sure that some killers have passed polygraphs. That includes people like Adrian Prout, Joseph Cambron, and Jeffrey MacDonald. But those people aren’t serial killers, i.e., people who’ve killed many people over a long period of time and in a methodological fashion.

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In fact, we only know of one serial killer who was given a polygraph and passed: Gary Ridgeway, the Green River Killer. In 2003, he pled guilty to murdering a staggering 48 victims in the ’80s and ’90s. Police gave him a polygraph test early on in their investigations in 1984, but he passed. Usually, like in the case of Jeffrey Dahmer, an abundance of physical evidence rules out the need for a polygraph. Not so in the case of Ridgeway. As for why he passed, maybe it was because of a psychopathic lack of anxiety. But since psychopaths don’t know what certain emotions feel like, Ridgway and others might never be able to tell us.