That's what they want you to believe, but he was as guilty as souce is being nooga.
He was a chess player. It was all a chess game.
The story was narrated, but not by him. By Red.
He gave valuable financial help to the guards. And got nothing in return?? Lol. Red even said "at first I thought he was trying to curry favor". Hint....hint... Of course he was.
The interactions perceive between the warden and Andy are based off what Andy tells Red and the others. Red was never around Andy and the Warden together, Red narrates what Andy tells him.
His ultimate work of art or move in his chess game was Tommy.. he spent months with Tommy "teaching" him and planting that whole story about his alibi in his head.
That's why that movie is in my top 5 of all time. Brilliant.