Part of the film was directed (uncredited) by Anthony Mann.
Technical advisor for the film was Sgt. Marty Wynn of the Los Angeles Police Dept. During the course of shooting he fell into conversation with Jack Webb, then the star of radio's "Jeff Regan, Private Investigator", who had a small part in the film. Wynn suggested that Webb do a radio series based on actual police files. Thus was born the idea for "Dragnet," which debuted on NBC radio about four months after this film was released.
This film served as something of a template for "Dragnet," which debuted on radio the following year, right down to the "this is the city" style opening narration, and the fact that a disclaimer appears at the beginning informing the audience that the names have been changed to protect the innocent.
This was an historical film in that it was the first to use the Los Angeles underground sewer and storm-drain system and its series of canals and tunnels as a backdrop.