The Enforcer/Murder, Inc. (1951)

Dist. Atty. Martin Ferguson (Humphrey Bogart) has the chance to send criminal Albert Mendoza to the electric chair. He depends on the testimony of Mendoza's right arm; Joseph Rico. But, Rico's so scared, he commits a mistake and dies. Ferguson pours over the case, again, and again, trying to find any new evidence, or witness, he might've missed. Through flashbacks, Ferguson sees what happened, up until Rico's death.

IMDb: https://www.imdb.com/title/tt0043503