For the past century the “lie detector” has been an iconic image in popular culture. The notion that we can strap someone into a machine and be able to know for certain if they are lying or telling the truth has been something that civilizations have sought for centuries, and the modern version—the polygraph—has some surprising history to it.

There are three men who had a huge impact on the development of the controversial modern machine, and each of them made significant strides in trying to find the truth.

William Mouton Marston

Marston was a Harvard psychologist who wanted to study blood pressure and the effect that lying had on the physical reading. Of course, as Gizmodo notes, the early lie detector wasn’t his only invention, Marston also had a huge impact on popular culture by creating the comic book series Wonder Woman. His first machine would measure blood pressure after each question he asked, not far from the modern polygraph machine that many are familiar with today. This first technique was essentially no more than a blood pressure cuff and an interrogation though.

John Larson

John Larson was a PhD living in Berkeley, California in 1921. He had particular interest in both creating better ways for police to interrogate suspects without intimidation or violence and a fascination with the ideas of Marston and other previous failed attempts to create a functioning lie detector.

Larson developed a device that most closely resembles the modern polygraph we see in police shows and have available for use today. He had the idea of incorporating more physiological elements such as perspiration and heart rate, while also developing a way to keep the readings fluid. With Marston, it would be question followed by reading, but with Larson the readings and the questions could happen simultaneously.

Leonard Keeler

Excited by the invention of Larson, Keeler took what he had done, made some minor adjustments and became the device’s biggest proponent. Encyclopedia credits him as the developer of the Polygraph, pushing its usefulness in law enforcement and even founding a school to study the usefulness of the machine and train a generation of Polygraphers.

For the machine itself, Keeler is credited as adding a galvanometer to measure the skin’s electrical resistance. Effectively adding another dimension to add the polygraph’s credibility. He also used it in the infamous Ohio serial killer case, “The Mad Butcher” and played himself in a film called Call Northside 777 that covered the true story of the use of a polygraph machine in freeing an innocent man.