Darryl F. Zanuck showed Fuller, who was then under contract to 20th Century Fox, a script by Dwight Taylor called "Blaze of Glory" about a woman lawyer falling in love with a criminal she was defending in a murder trial. Fuller liked the idea but knew from his previous crime reporter experience that courtroom cases take a long time to play out. Fuller asked Zanuck if he could write a story of a lower criminal and his girlfriend that he originally titled "Pickpocket" but Zanuck thought the title too "European". Fuller had memories of South Street from his days as a crime reporter and came up with his new title. Fuller met Detective Dan Campion of the New York Police Department to research the background material of his story to add realism, with Fuller basing the role of Tiger the police detective on Campion who had been suspended without salary for six months for manhandling a suspect.