Call Northside 777 (1948)

Synopsis
In this documentary-inspired thriller, P.J. McNeal (James Stewart) is a reporter who is asked by his editor to look into a potential story: their newspaper has been carrying an ad offering a substantial reward for information regarding the murder of a policeman that occurred eleven years ago. It turns out the ad was placed by a cleaning woman named Tillie Wiecek (Kasia Orzazewski); her son Frank (Richard Conte) was convicted of the crime, but she is thoroughly convinced her son had nothing to do with the killing. McNeal doesn't believe for a moment that Frank could be innocent, but he sees a good human interest story in Tillie and writes a piece that receives a great deal of favorable attention. Brian Kelly (Lee J. Cobb), McNeal's editor, thinks there might be more to this story and asks P.J. to look into the original murder case. To McNeal's surprise, Frank passes a lie detector test in which he proclaims his innocence, and the more he digs into records on the case, the more he finds wrong with the original investigation; some evidence is missing, much is inconclusive, and the reporter begins to wonder if Frank might have been railroaded after all, or if the police might be trying to keep something quiet. Call Northside 777 was based on a true story. ~ Mark Deming, All Movie Guide