1935day.year
Leonarde Keeler administers polygraph tests to two murder suspects, the first time polygraph evidence was admitted in U.S. courts.
Leonarde Keeler conducts the first polygraph tests admitted as evidence in U.S. courts, pioneering lie detector use.
In 1935, psychologist and criminologist Leonarde Keeler introduced the polygraph to American law enforcement.
On February 2, he administered tests to two murder suspects in Chicago, marking the first time polygraph evidence was accepted in U.S. courtroom proceedings.
The device measured physiological responses—blood pressure, pulse, and respiration—to infer deception.
Keeler's innovation captured public interest and laid the groundwork for forensic science advancements.
Though polygraph reliability remains debated, this event set a precedent for investigative technologies in criminal justice.
1935
Leonarde Keeler
polygraph tests