They do it for hiring and then randomly after that.
Answered - Pre-Release Instructor (Current Employee) - McFarland, CA
Pre employment and random
Answered - Custody Officer (Current Employee) - Plainfield, IN
Yes. Urine test
Answered - Security Monitor (Former Employee) - Houston, TX
Random drug testing for any employee
Answered - Program Counselor-Special Offenders Unit (Current Employee) - Philadelphia, PA
Just don't do drugs and you'll be fine.