During his convalescence from an illness in his adolescence, Keeler was introduced to the Berkeley Police Department and to August Vollmer, pioneer in the fledgling scientific crime detection methods known as the lie detector, on which experiments were being conducted. Keeler instantly saw its beneficial uses in law enforcement for investigative purposes. His skill in the use of the instrument and his interpretations of many examinations using the polygraph ensured its acceptance by the overwhelming majority of law enforcement agencies in the U.S. and around the world. He was the originator of the Keeler polygraph technique, which has remained essentially unchanged since his death in 1949.