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.
The killer lives in Hollywood in a bungalow court along Santa Monica Blvd. between Fuller Avenue and Poinsettia Place. The Movietown Plaza shopping center would later occupy this location for many years. It was subsequently replaced with a mixed-use residential and retail complex called Avalon West Hollywood, completed in early 2017. The neighborhood had become part of West Hollywood when it was incorporated in 1984.
Loosely based on the real-life 1946 crime spree of Erwin "Machine Gun" Walker (1918-1982). Unlike the character in the film, Walker was captured, tried and sentenced to death for first-degree murder. On April 14, 1949, two days before his scheduled execution, Walker attempted suicide and the execution was postponed. A psychiatric board pronounced him insane and he was sent to the Mendocino State Hospital for the next 12 years. Declared sane again in 1961, his sentence was commuted by the governor to life without parole. From 1970-74 he filed several motions to appeal his case, twice making it to the California Supreme Court. The second time the court vacated the "without parole" part of his sentence. Walker applied for and was granted parole in 1974. He then legally changed his name, worked as a chemist and died in 1982.
The subterranean chase scenes in this film convinced a Warner Bros. executive to use the storm drain tunnels under Los Angeles for the climactic scenes in Them! (1954). That film's original story idea to have the giant ants invade New York City's subway system was scuttled partly due to budget constraints, but mainly because of the horrified reaction of NYC transportation secretary William J. Daley to such a suggestion.
The three fired cases were head stamped 380 AP RMC which means .380 Automatic Pistol Remington Metallic Cartridge. That cartridge at that time was fired in a Colt 1903 semi automatic pocket pistol and several European semi autos. It is not fired in a revolver and was not a common cartridge.
The shots of two patrol cars pulling into the police station would later be reused in The Big Combo (1955). He Walked by Night (1948) and The Big Combo (1955) were shot by the same cinematographer, John Alton.