Idon't really know but I know an easy way to escape WITHOUT going through the tunnel or using the lockpick Just go Magic>Destruction>Flames. Then just shoot the flames ouside your cell. A guard should open the door to attack you. You can kill him or just run.
I used my mage to kill the guard through the bars. I then proceeded to kill every guard and civilian in the prison. After which, I ran outside. A gaurd greeted me with,