And the Lie-Detector Determined...It is Pseudoscience!

Though portrayed in movies and TV shows as infallible, the polygraph is not as reliable a machine as you may think.

BY: MICHELLE KRASOVITSKI

I’ve been interested in true crime ever since I was 12, after I accidentally stumbled onto the A&E channel when I was searching for TLC in hopes of spending the evening watching marathons of Say Yes to the Dress. I don’t remember which specific show it was—think along the lines of Forensic Files or 48 Hours Later—but I remember the gist: cheesy reenactions with obvious props and cheap-looking fake blood, a morose narrator outlining the final moments of a blond housewife’s life, a uniformed detective confirming that “nothing like this” has ever happened in their town, and, most importantly, that “aha!” moment that anointed the husband the killer, made obvious to everyone, even a 12-year-old like me. That “aha” moment is what makes true crime so compelling and so addicting to consume: it can range from a fingerprint match to a DNA link to a guilty verdict from a polygraph. It is something that neatly concludes a mystery and gives purpose and explanation to the unknown.

But what if this moment—one which, for better or worse, wraps up the case in the eye of the general public—isn’t as neat or as accurate as we like to think? 

I am of course referring to lie detector tests. Polygraphs usually occur right before, if not at, the climax of a true-crime story: the detectives have zeroed in on a suspect and this device, with its blood pressure cuff and rubber tubes, will give them a definitive answer as to the guilt—or lack thereof—of their subject. The issue is: lie detectors are not as accurate as TV shows, movies, podcasts, and famous court cases have made us believe. 

First developed in 1921 by John Larson, who had developed a way to measure respiration, heart rate, and blood pressure, the modern-day polygraph operates in a similar way, though now it is more computerized and integrated into technology. In addition to the initial points of research, lie-detector tests today look for respiration and perspiration. That is to say: how do you breathe and where do you sweat—and can any of this prove that you’re lying? This is of course a simplistic explanation. 

For crimes, most modern polygraphs employ the Control Question Test technique: questions pertaining to the specific crime as well as basic, casual questions (“did you eat breakfast today?”) are asked to establish a baseline. The idea behind the lie-detector test is that any variation from baseline, be it in the pulse or breathing, is a biological admission of guilt. This seems like a logical progression, however, there has never been a concrete study on the physiology of lying—meaning that there is no empirical evidence to suggest that a heightened pulse is evidence of dishonesty instead of being just that: a heightened pulse. 

It is funny to think about the scientification of lying; not since Pinnochio’s nose have we put so much of our faith into a system that claims it can reveal deception. Think about how you lie and think about the reasons for it: sometimes you even lie to yourself—promising, for instance, that you were going to the mall just to browse even though deep down you knew you intended to buy a pair of jeans. 

Despite what A&E shows may suggest, the validity of polygraph results has been debated for decades. In United States vs. Scheffer in 1998, the American Supreme Court ruled that polygraphs couldn’t be used in some federal courts because there was “no evidence that polygraph evidence is reliable.” 

And yet, the lie detector is ingrained into our public consciousness, seen as an objective arbiter of truth and deception. Most of us grew up watching the Maury Povich show, a tabloid talk show where host Maury puts guests on the spot, sometimes revealing paternity tests, other times subjecting his guests to polygraphs to reveal infidelity. It is clips of the latter that often go viral: Maury, glasses on the bridge of his nose, sat in his chair, going through cards and announcing either that “the lie detector determined that was a lie” or that “you are telling the truth.”

Buzzfeed and Vanity Fair YouTube series featuring Lie Detector Tests

And so you don’t have to be a true-crime fiend like me to know of the reverence of the polygraph: the little machine appears everywhere, from day-time trash TV to comedy movies to even YouTube—there are Buzzfeed and Vanity Fair series where internet personalities and celebrities are strapped to lie-detector machines and asked embarrassing questions. Though this is mainly played for humour, it serves to establish a cultural norm: the lie detector is the truth-serum technologized.       

Let’s return to Pinnochio for a moment to reveal the flawed thinking behind the blind trust of the polygraph. Pinnochio’s nose is a part of him, directly connected to his body, his brain, and thus, his mind. There is no moment where the audience doubts Pinnochio because we understand that his lie-revealing system is a natural part of his body. Yet, if Pinnochio’s creator Carlo Collodi (or Geppetto, if you’d like to stay in the cannon) had given him a system similar to the polygraph—that is to say, a third-party; something that is not a biological part of his being—we would rightfully be skeptical. After all, how could we be certain that an alien machine could detect his true intentions? Yet in real life, we rarely attribute this sort of skepticism to the polygraph, if at all. 

Image courtesy of Disney

It is very important that we take polygraph results with a grain of salt: the entire premise of “innocent until proven guilty,” upon which our justice system is built, is corrupted if we allow the simplest of pseudoscience to shift our perspective. There have been countless Netflix docuseries showcasing mishandled or error-stricken forensic science: from How to Fix a Drug Scandal to Exhibit A and The Staircase. It is in the latter that infamous blood-spatter analyst Duane Deaver was featured: Deaver falsified hundreds of blood-spatter evidence over several decades and landed several people in prison. His most egregious case is one where he purposefully misrepresented a man’s blood, placing it at a crime scene where he had not been, resulting in an 18-year-sentence. 

This is all to say: the truth is a complicated matter. Even the things that we believe are objectively scientific—DNA taken from hair, blood evidence, and of course, the polygraph—can be altered if not just misrepresentative of the truth. The blind trust placed in polygraph results is similar to the Twitter-scrollers who read a headline of an article and believe they’ve understood the gist, missing a lot of important information that is included beneath the black, block-lettered banner. Next time you watch a documentary or a true-crime series and hear the results of a polygraph test, ask yourself this: do you really want your judgement of a human being to be based solely on a test that can be wrongly-passed with a simple Google search and enough effort?