Leonarde Keeler (1903–1949) was the co-inventor of the polygraph. He was named after the polymath Leonardo da Vinci, and preferred to be called as ‘Nard.’ He was a Berkeley high school student and amateur magician. He was captivated by John Larson’s machine – his so-called ‘cardio-pneumo psychogram,’ capable of detecting deception, and worked on to produce modern polygraph.
In 1924, Keeler’s first handmade polygraph instrument, which he called “the Emotograph,” was destroyed in a fire at his residence. On February 2, 1935, he conducted the first use of his invention, the Keeler Polygraph—otherwise known as the lie detector. Keeler used the lie detector on two criminals in Portage, Wisconsin, who were later convicted of assault when the lie detector results were introduced in court.
In 1938, Keeler conducted a polygraph test upon Francis Sweeney, the chief suspect in the Cleveland torso murders. Sweeney failed to pass the test, leading many to believe that he was the culprit; however, due to lack of evidence, Sweeney was never charged with the killings.
He above all was most instrumental in the popularization of modern polygraphy in criminal investigation and job screenings. He went as far as appearing in person in the 1948 film noir docudrama, Call Northside 777 with James Stewart, Richard Conte, and Lee J. Cobb, playing himself.
Keeler moved to Chicago in 1930 to work in the Scientific Crime Detection Laboratory at Northwestern University and ultimately became the head of the laboratory 1936. He held that position until 1938 when he entered private business. Leonarde Keeler opened the first polygraph school, known as the ‘Keeler Institute.’ He became the first full-time private polygraph consultant.