He was captivated by John Augustus Larson's machine, a "cardio-pneumo psychogram", with the goal of detecting deception, and worked on it to produce the modern polygraph.

He moved shortly after that to enroll in UCLA to follow Vollmer who accepted a new job as the Chief of Police for Los Angeles.

[4] 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.

[8] Later on, she established her own all-woman's detective agency in Chicago, specializing in forensic investigation, and left Keeler to marry another man, Rene Dussaq, and during World War II joined the WASPS (Women's Auxiliary Service Pilots).

Devastated by his wife's departure and later death, Keeler died in 1949 in Door County, Wisconsin, at the age of 45, after suffering a stroke brought on by stress, alcohol, and cigarettes.

[9] His contributions to the development of the polygraph are featured in the documentary film The Lie Detector which first aired on American Experience on January 3, 2023.