When Wagner tells Frankie that Lenny has plead guilty to violating the "Sullivan Law", he is referring to New York City's Sullivan Act of 1911 which makes possession of a concealable firearm a misdemeanor and possession in public a felony, unless a permit has been issued by, and at the discretion of, the New York City Police Department.
The bridge at the beginning of the film is the Queensboro Bridge, looking from Manhattan into Queens across the East River.
The Reginald Rose story originally aired on television on March 8, 1955, as part of the anthology series The Elgin Hour (1954) (The Elgin Hour: Crime in the Streets (1955)). John Cassavetes and Mark Rydell were members of the cast of the TV version with Robert Preston in the James Whitmore role and Glenda Farrell in the Virginia Gregg one. Will Kuluva repeated his role in the movie as Mr. Goia.
Don Siegel says in his autobiography that he argued much on the set with actor Mark Rydell because he did not shoot Rydell's face enough.
Sal Mineo (Angelo Giola) and Will Kuluva (Mr. Giola) portray a father and son in this film. They previously portrayed a father and son in the episode "The Garcia Case" of the TV Series, "Janet Dean, Registered Nurse" (1954)
Sal Mineo (Angelo Giola) and James Whitmore (Ben Wagner) later appear together in "The Young Don't Cry" (1957)