The Shawshank Redemption takes place during the 1940s and 1950s. The world was a different place during this time. Prisoners did not have the same rights they do today. There were also less ways to prove someone innocent or guilty. There was no DNA and gunshot residue tests weren't invented yet. Andy Dufresne looked fairly guilty to a jury during the 40s. Andy was treated with the same harshness as any man convicted of murder would have been during his time. It is Andy who begins a profitable relationship between himself and the guards. He is the one to suggest helping them with their taxes and better ways to hide the bribes they get. Many powerful men, like the warden, would probably have received this type of bribe money during this time period. When the warden finds out that Andy is undeniably innocent, he cannot simply tell the proper authorities because Andy already knows his dirtiest secrets. Men of power often treat people poorly to keep their secrets safe.