There is no Yuma Prison. There is the Arizona Territorial Prison.
Vince Harper would still have to go back to prison to face charges for breaking out, guilty or not. He would also have to face charges for assaulting and robbing the man on the trail. There would also be charges for resisting arrest and attempted murder by shooting at the prison guards and Hollister. There is no way he would walk free even if he was proven innocent of the murder.