The Man Who Talked Too Much (1940)

Assistant District Attorney Stephen Forbes, an impressive orator with a long list of convictions, resigns after an innocent boy is convicted and the real murderer confesses too late. He opens a cheap law office and his secretary Joan Reed goes with him. Business is bad until he ties up with J.B. Roscoe, the contact man between city hall and the underworld. Forbes moves to a swanky office and adds two people to his staff - his younger brother John, who he helped through law school, and Celia Farraday. Celia helps John win his first case and the two fall in love. John realizes his brother's firm isn't honest and wants to break the underworld contact. He opens Steve's safe for federal authorities hunting evidence against Roscoe. But the latter plants enough circumstantial evidence against John that he is convicted of murder and sent to death row.