Would Some Ambiguity Be Good Or Bad?

I was thinking about the Shawshank Redemption last night. The movie version anyway, since I haven't read the story it's based on. In particular, I was thinking about Elmo Blatch. He's the character that Tommy tells us about, his cellmate in a different prison, who admitted to killing a golf pro and a woman he was with. Elmo goes on to mention that the murders were pinned on the husband of the woman, a hotshot banker. All of which is rather interesting to Andy Dufrense, since he's in prison for allegedly killing his wife and the golf pro she was having an affair with.

So consider the effect that has on the story. Though the warden dismisses the story as Tommy trying to cheer Andy up, I think we're supposed to believe that it's something that actually happened (in that particular fictional universe), which would mean Andy was, in fact, innocent. In that event, Andy can I believe be seen as justified for his breakout, and his swiping of the warden's ill-gotten gains, especially since he ruins the warden and the chief guard as a parting gift.

Now remove Elmo from the equation. All we know of what happened is that Andy was sitting in his car outside the place the golf pro and his wife were shacked up in, holding a gun, and drunk as a skunk, and that he got out and started towards the house. Without Elmo, all we have is Andy's insistence that he's innocent, without anything to back it up other than the fact we didn't see him actually do it. At that point, Andy could be just another one of the cons in Shawshank, always insisting they're innocent, with a wink and a nod as they say it. Andy never acts much like a man who has been wrongfully imprisoned, he mostly just accepts that this is the hand he's been dealt, and does what he can with it.

Of course, without the introduction of Elmo, Tommy probably doesn't get shot, and we'd have to wait for a different stimulus to prompt Andy's escape. Still, I don't doubt that Andy would leave at some point, given how long he'd been working on that tunnel. It might just come to pass that Andy decides to leave after one day where the food is particularly bad, or he sees a guard mistreat another prisoner, or who knows what. But without the specter of Elmo (and the death of Tommy), do we see Andy's escape in the same way? For all we know, he's a murderer. Does everything he did in establishing that library, and helping prisoners get their high school equivalency offset that fact? If he still screws over Warden Norton in this process, does that color how we would see it?