I'd agree with hope being the most powerful theme found in the movie and many movies like it. The need to see justice gets the blood pressure going throughout the film and pays off at multiple points. Prison films play on that quite a bit, whether it is Shawshank, Green Mile, Cool Hand Luke, The Last Castle, Bridge over the River Kwai etc... Whether you decide to give the audience the justice and your characters the hope can totally change the feeling of the film.

The theme is the battle between hope and fear. Everything in the movie plays to this single theme.

Justin, your comment reminded me of that Orson Welles quote: "If you want a happy ending, that depends, of course, on where you stop your story." If the story had stopped with Tommy's assassination... if the story had stopped with Andy's escape... completely different movie. Re justice: Remember when we were kids, how often we heard or said, "It's not fair!" Fairness is something deeply ingrained in us from our childhood. And justice is tethered to fairness. Having Andy and Red reunite on the beach in Mexico is such a satisfying ending because in the end, it is ultimately the fair ending.

Hope and fear is an interesting tandem, Michael. It reminds me of how Peter Docter at Pixar originally had Joy paired with Anger, but then eventually realized the opposite was Sadness. To me, it's Hope and Despair / Cynicism. I can see Fear at work in that equation as Despair may be a way of hiding one's Fear, a safe way of shrouding one's fear by wrapping it up in Cynicism.