Innocent people do have something to hide: their private life. The "right to be left alone" is, in the words of the late Supreme Court Justice Louis Brandeis, "the most comprehensive of rights and the right most valued by civilized men." Analysis of a person's urine can disclose many details about that person's private life other than drug use. It can tell an employer whether an employee or job applicant is being treated for a heart condition, depression, epilepsy or diabetes. It can also reveal whether an employee is pregnant. This can affect one's chances of getting hired or not.
Urine tests are body searches, and they are an unprecedented invasion of privacy. The standard practice, in administering such tests, is to require employees to urinate in the presence of a witness to guard against specimen tampering.
In the words of one judge, that is "an experience which even if courteously supervised can be humiliating and degrading." Noted a federal judge, as he invalidated a drug-testing program for municipal fire-fighters, "Drug testing is a form of surveillance, albeit a technological one.