He is in prison as as opposed to jail I presume. It then becomes a question of parole, the nature of the offense and his conduct while in prison.
You can write a letter to the parole board if you so desire, but he will have to serve the minimum term of his sentence.
Not much can be done. Speak to a criminal attorney for more specific advice. I would contact the legal aid society of Cleveland. It probably won't make a difference, unless he has kept his nose clean inside and participated in rehabilitation programs.