Tremors in the Blood review: The intriguing origins of the polygraph

Amit Katwala's thorough history of the lie detector test looks at its inventors and some of its earliest cases, placing it, warts and all, in its historical and scientific context

Humans



13 April 2022

By Chris Stokel-Walker

The polygraph test looked scientific because it was based on physiological readings

Peter Dazeley/Getty Images

Tremors in the Blood

Amit Katwala

Mudlark

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THE polygraph test has been used in criminal prosecutions for decades – a silver bullet for police and prosecutors alike. Measuring heart rate, breathing speed and the conductivity of skin, it is supposedly infallible and given the respectable veneer of science in a courtroom. Someone who flunks the test must be lying, their body’s tell-tale signs betraying their deepest secrets.

Yet that is far from reality. “There is no single tell-tale sign of deception that holds true for everyone – no Pinocchio’s nose,” writes Amit Katwala in Tremors in the Blood. A misfiring test has real ramifications: the US-based National Registry of Exonerations holds records of more than 200 people who failed a polygraph test, were convicted of a crime and imprisoned, but were later found to be innocent.

Katwala’s book traces the test’s history, looking at the early adopters of the technology and some of its earliest cases. The book goes back a century, telling the story of John Larson and Leonarde Keeler, co-inventors of the polygraph (called the emotograph by Keeler), and August Vollmer – all three key to its adoption by US police forces and later worldwide.

Larson was a complex character, breathed back to life by Katwala’s meticulous research. A bookish, morally driven individual, Larson joined the Californian police force in the early 1920s. Unlike the high school dropouts and extortionists who filled the force’s ranks then, Larson was the only police officer in the US with a PhD, in physiology. He would work in university labs by day and police the streets at night.

Larson’s master’s thesis had been on the relatively new technology of fingerprint identification, which had recently become admissible in court. He thought there were still more ways of catching criminals. He was lucky to work under a police chief, Vollmer, who was more bookish than he liked to let on.

Vollmer was equally driven to do the right thing, and was constantly trying to improve policing. In 1921, after reading an academic paper by a psychologist and lawyer who had tested whether his friends were lying based on their blood pressure readings, Vollmer asked Larson to develop a machine that could do the same. The result was mocked by fellow officers, and described in newspapers as looking like a combination of radio, gas stove, stethoscope, dentist’s drill, barometer, wind gauge, time ball (an old form of clock) and watch – but it appeared to work.

Katwala vividly portrays those heady early days when the polygraph seemed to catch out liars. Then, he deftly delivers the twist in the tale: 40-odd years after cobbling together the first machine, Larson forswore his invention because of the way it was used. It was “nothing more than a psychological third degree aimed at extorting confessions, as the old physical beatings were”, he said in an interview – far removed from his meticulous scientific approach.

The book captures the wonder of scientific breakthrough – and what happens as the story becomes more complex. In 1965, the year Larson died, the US House Committee on Government Operations warned that the world had been hoodwinked by “a myth that a metal box in the hands of an investigator can detect truth or falsehood”.

Yet the polygraph is still being used. In 2021, the UK began polygraph testing people convicted of terrorism offences and, later that year, convicted domestic abusers, despite the fact there are serious doubts about whether it works.

Why has the polygraph remained on its pedestal? Perhaps because no one, until now, has placed it, warts and all, in its historical and scientific context.

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