Eliza, in the US the people who are employed in the prisons have earned the 'right' to work and often are eligible to be released within a foreseeable time. The incorrigible and violent have not earned the right.

Even then, a significant number of workers have walked off and been free for a period of time. When they are caught, they are no longer eligible to work.

A little story here that made me smile: At a house museum I managed, a curio cabinet was commissioned at the local prison. The day it was delivered, the inmate who actuallly built it and his 'supervisor' carried it in.

At one point the supervisor was talking with staff while I watched the inmate affix a small hasp to the front of the cabinet. When he was done, he said to me with a smile: Well, that'll keep the good guys out.