The documentary explores the checkered history of lie detectors

The documentary tells the story of noble intentions and sinister consequences. John Larson, one of its inventors, was a medical student and law enforcement officer looking for more humane methods of policing and interrogation. He brought new scientific and psychological ideas to create the device in 1921.

The technology that Larson and his co-authors used was still in its infancy, and the idea that people lied about measurable, consistent physical symptoms had not been proven.

It is still like that. Polygraph protocols have evolved, but detractors of the devices say they measure only anxiety, not truthfulness. And even as major organizations have raised questions about the tests’ scientific validity, and federal laws have barred most private employers from requiring them, the idea that dishonesty can be measured through physical testing has persisted.

The documentary suggests that the popularity of polygraph tests had more to do with publicity than accuracy, and over time Larson’s vision was overturned as polygraphs were used to intimidate, imprison and interrogate people.

With the help of expert interviews and a kaleidoscope of historical footage and images, director Rob Rapley follows the tale of his own creator’s invention compared to Frankenstein’s monster.

It’s a challenge, an eye-opener about the potential consequences of society’s desire to merge psychology and science, and a cautionary tale that says as much about the psychology of the concept’s proponents as it does those whose veracity they question.