Was the main guy in The Shawshank Redemption innocent?

Answer 1

Andy was innocent of killing his wife, the crime for which he was sent to prison. Another man killed Andy's wife and her lover, a Golf professional. Tommy told Red and Andy how another prisoner at another prison bragged to him about killing a golf pro and the wife a of a banker, and how the banker went to prison for his murder.

Answer 2

Yes, he was innocent, but was convicted because he looked guilty. He got drunk and planned to shoot his wife and her lover, but at the last minute he lost his nerve and decided not to. Purely coincidentally, another man shot the two adulterous lovers, that same night, with the same caliber gun that Andy planned to use (a .38). Andy threw his gun into a river, but even though law enforcement performed an exhaustive search of the river, they never found it.

Andy had no alibi (he went home alone to sleep it off), and since his gun couldn't be found, he couldn't prove that his gun did not fire the bullets (no comparison could be made between it and the bullets that killed the lovers). The evidence against Andy seemed overwhelming so the jury convicted him.