CALL NORTHSIDE 777 (1948)

Advertising pays, even in film noir. A tiny classified notice appears in a Chicago newspaper placed by an elderly scrubwoman. In it, she claims her son is innocent of the murder for which he has already served years of a life sentence and offers a reward to anyone who can help her prove it. Smelling a human interest story, the paper’s city editor (Lee J. Cobb) assigns ace reporter P.J. McNeal (James Stewart) to check it out. At first, the cynical reporter refuses, convinced after reading the trial records that Frank Wiecek (Richard Conte) got what he deserved. But as his investigation warms up, so does the reporter to the con's plight. Eventually, McNeal finds new evidence in Wiecek's favor (though of course not without bumps along the way), but it's all circumstantial. But then the single piece of hard proof needed to prove Wiecek innocent is revealed through a laborious photographic enlargement process (considered high-tech at the time, but today easily done on a smartphone). Based on a true case and shot in semi-documentary style on location, CALL NORTHSIDE 777 is well acted by all (especially the stalwart Stewart) and remains engaging and suspenseful even after repeated viewings.