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19 April 2022

How we fell in love with the polygraph

Amit Katwala, author of Tremors in the Blood, explains why we are gripped by “lie detectors” even though we know they don't work.

By Sarah Manavis

In an era where fact and fiction often blend alarmingly into one, what could be more seductive than the ability to objectively prove a lie? The polygraph test — often known by its misnomer, the lie detector — has made us this promise since it was invented in 1922. And yet, 100 years on, we’re no closer to having a device that can achieve this aim. So why, despite repeated failure, can’t we give up on the idea of certain truth? 

The answers can be found in Tremors in the Blood: Murder, Obsession and the Birth of the Lie Detector, a new book by the journalist Amit Katwala on the history of the polygraph. The title is taken from Daniel Defoe: “Guilt carries fear always about with it; there is a tremor in the blood of a thief.” With a cinematic narrative style that often reads more like a thriller than a work of history, the book chronicles the murders, affairs and intimate relationships at the police precinct in California where the polygraph was invented. Katwala charts how the machine tore apart the lives of the men who invented it, and explores how it led to the deaths of many more who failed to pass its test.

Katwala is a senior writer at the technology magazine Wired, where he writes about the intersection of science and culture, and is the author of The Athletic Brain: How Neuroscience is Revolutionising Sport and Can Help You Perform Better. His interest in writing about the polygraph was ignited four years ago, when he watched a man wrongfully convicted of murder take a test in Netflix’s Making A Murderer.

“My bullshit detector went off,” he tells me, from his home in London, via Zoom. “I started to dig into the cases, and the stories were so mental that I couldn’t not write about it.” In the Guardian he investigated “the race to create a perfect lie detector — and the dangers of succeeding”, and he spent the pandemic combing through pulpy, hundred-year old magazines and travelling to the United States to trace the steps of the polygraph’s inventors.

At the heart of Tremors is the murder of Anna Wilkens, a housewife who was shot at point-blank range during a roadside robbery in Berkeley, California, in 1922. Her husband, Henry, was accused of orchestrating the murder. While the investigation was continuing, Berkeley’s police chief, Gus Vollmer, had introduced his teenage protege, Leonarde Keeler, to a 28-year-old officer in his precinct, John Larson. Larson, the US’s first policeman with a PhD, who was working on a complex invention that could almost always catch a lie. From here, Tremors details how Keeler and Larson built the polygraph, and tried and failed to overcome the machine’s fundamental flaw: it could not accurately do its job.

The timing of the book‘s publication seems particularly apt. Katwala notes that, a century after the polygraph’s invention, we’re in a “golden age of lying”: from Trump’s presidency to a cultural obsession with “scammers”. He also observes that the polygraph was first invented in similar global conditions.

“There was the [Spanish flu] pandemic, the world was at war, there was a cost-of-living crisis and it was a time when it felt like there was a lot of territory up for grabs,” he says of the US in the 1920s. “All these things were being invented, there were all these discoveries and there was a huge amount of money to be made if you were smart enough to use that new knowledge to create a product that people wanted. It was a Wild West, a mad race to make money.”

Perhaps these contextual parallels can help to explain why the polygraph’s use in the UK is on the rise, particularly in the Home Office and in British policing, where pilot programmes have been adopted this year to test convicted terrorists and sex offenders. “It’s a way for the government to signal that they’re taking action and clamping down on terrorism,” Katwala explains. “It’s hard to argue against. Who’s going to stand up for the rights of sex offenders and terrorists?”

Katwala insists that no one uses the polygraph because “they think it’s going to give us the best results, it’s because whoever’s in charge thinks it’s going to make them look tough on crime”. He asks: “Why would anyone be using a 100-year-old piece of technology that’s been repeatedly debunked in 2022, if not to signal to your base that you’re taking action? It’s easy for people to understand, it’s headline-grabbing, and whether it actually works or not is sort of a moot point.”

Katwala feels that there is only a narrow set of circumstances in which a polygraph could be used appropriately. “I don’t think it’s completely unjustifiable to use it with sex offenders, for instance, but I don’t think it should be used in the context of being a lie detector. It should be used as what it is, which is essentially a measurement of emotional arousal, and that’s quite a useful tool, as a part of a suite of other tools that you might use when interviewing someone.”

There is no guarantee that emotional arousal means someone is lying, and the polygraph is relatively easy to beat. Katwala compares it to a lateral flow test — something that has relatively low accuracy. “As long as you’re aware of the limitations of a test, and you take that into account, then I wouldn’t say it should never be used in any official setting.” He argues that such circumstances function as the “thin edge of the wedge”, however. Once the polygraph is deemed acceptable in certain contexts, its use will simply expand.

“It starts off with marginalised groups or even convicted criminals, and then it starts getting wider and wider and it starts getting used in job interviews, and then it starts getting used in regular police interviews and then it’s everywhere, and you get into a situation like in the United States, where it’s believed the tests are clear and it’s a de facto part of the justice system,” he says.

As Katwala neared the end of writing Tremors, he became aware of the societal impulse to treat technology “as a sort of God”. “I’m not anti-science, but I’m anti-pseudo-science and anti ‘technology will save us’,” he says. “The polygraph is a symptom of our belief that technology is going to save us, that AI is going to solve all our problems.”

He says that if the polygraph were to be invented now it wouldn’t have been designed by two relatively anonymous police officers. “Keeler and Larson would be the stars, they’d be like Elizabeth Holmes [the founder of Theranos], they’d have tens of millions of dollars in funding,” he says. “It would be an app, right?”

With this in mind, the question remains: despite not ever being a true “lie detector”, why does the polygraph maintain its grip on public consciousness, an idea we can’t give up on?

“It’s more about society than it is about the machine itself,” Katwala says. “If it hadn’t been the polygraph, it would have been some other spurious technique. The fact that there’s other new forms of lie detector being invented all the time kind of shows that.

“It’s hard to live in a world where you don’t know what’s real and what’s not, but it’s the world that we have to live in. The promise of a machine that tells the truth was always compelling, and I think it always will be.”

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