Lie Detector

This article was originally written and submitted as part of a Canada 150 Project, the Innovation Storybook, to crowdsource stories of Canadian innovation with partners across Canada. The content has since been migrated to Ingenium’s Channel, a digital hub featuring curated content related to science, technology and innovation.


Nova Scotia-born John Larson was a young medical student in California in the 1920s when he invented the modern lie detector. Working from a psychological test that had been developed at Harvard in 1915, he developed a procedure that involved noting a person’s answers to a series of carefully worded questions while recording blood pressure, skin temperature and breathing rate. By interpreting the responses, a trained technician could theoretically deduce which answers were truthful and which were not. Many improvements have been made to the process since Larson’s invention was first used by Berkeley police in 1921, but the lie detector remains a controversial tool in the world of crime-solving. Over time, Larson himself came to question the reliability of his own device eventually referring to it as “Frankenstein’s monster.”

Newspaper reporters were the first to use the term “lie detector.” Larson and fellow operators objected to the name, but it stuck. His original machine is at the Smithsonian Institution in Washington, D.C.

John Larson ended up marrying the first person he ever interrogated using his polygraph machine. Margaret Taylor was one of the victims in a college dorm robbery he had been brought in to solve. He found the thief (another co-ed) – and a wife – thanks to his invention. The fairytale storyline made the newspapers and also wound up as part of the plot of a Dick Tracy comic strip.

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Janis Nostbakken