The producers struck a cross-promotional deal with the then-popular clothing store Ohrbach's. In exchange for having Ruth Roman's character be an employee of the store, Ohrbach's agreed to provide most of the female characters' costumes.
At the end, it can be seen how bad the Los Angeles smog was at that time. It sometimes was difficult to keep one's eyes open due to the intense stinging of the smog.
This film was released about a year before Broderick Crawford began his most notable TV role, starring as Dan Matthews in Highway Patrol (1955). Two other cast members also would go on to be famous TV cops, although in a less serious vein. Claude Akins (Matty Pavelich) is Sheriff Elroy P. Lobo in B.J. and the Bear (1978) and The Misadventures of Sheriff Lobo (1979); Stafford Repp (the Boxing Manager who identifies Pavelich) is Chief O'Hara in Batman (1966).
FBI Director J. Edgar Hoover objected to the script that was submitted to him under the working title of "Case File: FBI." He not only was concerned about showing details of criminal activity but also the countermeasures the FBI used and that information could be used by criminals in the future to avoid arrest. It appears the producers alleviated Hoover's worries, and the title subsequently was changed as well.
Credited as writing both the screenplay and the source novel, "The Gordons" was comprised of husband and wife Gordon Gordon and Mildred Gordon. Together they wrote 19 books, mostly crime and mystery novels, but their most successful books were probably "Undercover Cat" and "Undercover Cat Prowls Again," the former being the basis for the Disney film That Darn Cat! (1965). The most accomplished film they were associated with was probably Blake Edwards' Experiment in Terror (1962), a tense thriller starring Glenn Ford and Lee Remick. Gordon Gordon was a former FBI agent.