trusty

luottovanki

luotettava reliable Reliable or trustworthy.
A trusted person, especially a prisoner who has been granted special privileges.
1941, James Howell Street, In my fathers house''

We usta have a rule that if a trusty shot an escaping convict, then the trusty would go free.

The cell block is clean and doesn't smell of disinfectant. The trusties do all the work. The supply of trusties is always ample.