The Alfred Hitchcock Hour (1962)

Ned Murray is a lawyer who gets Lew Rydell off on a murder charge, but later learns that he is guilty. Knowing that Lew cannot be tried twice for the same crime, Ned seeks out other ways to bring the man to justice. He talks to a gangster Tony Hardeman who misinterprets Ned's concern and decides to have Lew killed. Ned suspects that a murder is about to take place and tries to save Lew. He arrives at Lew's house too late and discovers that Lew is still alive. He managed to kill Tony before he could kill him. Ned realizes that he can now have Lew sent to prison since he can now be tried for another murder. Guilt overwhealms him, however, and Ned decides to defend Lew in court once again.