Bad Idea

I was watching MSNBC today and a program came on about life behind bars. Did you know that in some prisons inmates work on cars that belong to the staff of that prison? I don't think that is such a good idea. The guy working on the car doesn't really have anything to lose( the majority they talked to were in prison for murder) so if a guard makes him angry what's stopping him from cutting a brake line, or two?