Drug testing has become commonplace throughout much of the business community for a variety of reasons. Many corporations offer fairly liberal use of company cars and equipment, and they don't want to assume any more liability than is absolutely necessary when it comes to who uses that equipment. There is also usually an insurance incentive for companies taking preemptive measures to keep suspected drug abusers off the corporate roster. Law enforcement agencies are no less careful, but for different reasons.

Law enforcement agencies maintain a zero-tolerance policy for illicit drug use. Illicit drug use not only constitutes one of the biggest law enforcement problems in this country today, but also one of the top public health problems. Much time and effort, along with vast resources, are spent on tracking down illegal drugs and their sources. There are entire federal and state agencies, as well as police department divisions, that are committed solely to the elimination of illegal drug trafficking and use. In order to enforce the body of law that surrounds illegal drugs, officers and agents must be absolutely above reproach with regard to the use of such drugs.

Most pre-employment drug testing is done by using a urine sample. On rare occasions a blood sample is required. The authority for these tests actually comes from the applicants themselves. Routinely, on the application form that the applicant signs, usually somewhere in small print, is an authorization for testing. This gives the hiring authority the right to conduct these examinations and eliminates any chance for the candidate to withdraw permission for the testing. Certainly the applicant can refuse to take a drug test, but then the hiring authority can refuse to give that applicant any further consideration.