By the late 1950s film noir was dead but the juvenile delinquent thriller, originally inspired by the novels of Hal Ellson from ten years earlier ("Duke," "The Golden Spike," etc), was thriving on the B-movie circuit. But MGM and producer Pandro Berman, perhaps hoping to repeat their 1955 success with "Blackboard Jungle," tried to blow "Key Witness" up into an A-movie, widescreen Cinemascope, "Rebel Without a Cause" alumni (Hopper, Corey Allen), and all. Though the plot relies on sometimes ridiculous turns (in one maddening scene, a deputy runs into a courtroom interrupting testimony) and the characters are mostly cartoons (Muggles certainly lives up to the first syllable in his name), director Phil Karlson's decision to shoot on the streets of Los Angeles keeps everything moderately realistic. The opening scene, set in a hilly slum neighborhood just north of City Hall in the Chinatown area (though it looks like old Bunker Hill and is referred to as "East L.A." in the film), immediately puts the viewer into the middle of the action and the period. If this film had been shot on a soundstage, as "Blackboard Jungle" was, it would have fallen apart within the first ten minutes, but once again L.A. saves the day. If you love the atmosphere of on-location films from this era, you'll enjoy the sensation of sitting through "Key Witness."