From Psychemedics -
World's largest provider of hair testing for drugs of abuse
 

WHY IS DRUG TESTING VITALLY IMPORTANT TO CORRECTIONS DEPARTMENTS TODAY?

Community leaders raise serious concerns about armed officers under the influence of drugs.
Drug users are absent up to 16 times more often.
Drug users are 1/3 less productive.
Communities MUST have confidence that their police and corrections departments are drug free.

In surveys of drug abusers themselves: 

44% admitted selling drugs to co-workers 
18% admitted stealing from employers