Tremors in the Blood review: The exciting origin of polygraph

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


April 13, 2022

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

Peter Dazeley / Getty Images

Shaking in the blood

Amit Katwala


The polygraph test has been used in criminal cases for decades – a silver bullet for both police and prosecutors. Measures heart rate, respiration rate and skin conductivity, it is probably infallible and is given the respectable veneer of science in a courtroom. Someone who fails the test must lie, and their body’s check marks betray their deepest secrets.

But that is far from the reality. “There is no single sign of deception that applies to everyone – no Pinocchio’s nose,” writes Amit Katwala in Tremors in the Blood. A misfire test has real consequences: the US-based National Registry of Exonerations has records of more than 200 people who failed a polygraph test, were convicted of a crime and imprisoned, but who later turned out to be innocent.

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

Larson was a complex character, revived by Katwala’s careful research. A bookish, morally driven individual, Larson joined the California police force in the early 1920s. Unlike the high school dropouts and blackmailers who filled the ranks then, Larson was the only police officer in the United States with a doctorate in physiology. He would work in university laboratories during the day and police the streets at night.

Larson’s master’s thesis was about the relatively new technology for fingerprint identification, which has recently been allowed in court. He believed that there were more ways to catch criminals. He was lucky enough to work under a police chief, Vollmer, who was more bookish than he liked to sound.

Vollmer was equally driven to do the right thing and constantly tried to improve police work. 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 ridiculed by other officers and described in newspapers as a combination of radio, gas stove, stethoscope, dental drill, barometer, anemometer, time ball (an old form of clock) and clock – but it seemed to work.

Katwala vividly depicts those intoxicating early days when the polygraph seemed to catch liars. Then he skillfully delivers the twist in the story: About 40 years after assembling the first machine, Larson gave up his invention because of how it was used. It was “nothing more than a psychological third degree aimed at blackmailing confessions, as the old physical abuse was,” he said in an interview – far from his meticulous scientific approach.

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

Nevertheless, the polygraph is still used. In 2021, the UK began polygraph testing people convicted of terrorist crimes and later that year convicted domestic drug addicts, despite serious doubts about whether it works.

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

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