Random workplace drug tests are often inaccurate, do not prevent drug use and violate workers' right to privacy. Millions of American workers are tested yearly, even though they are not suspected of drug use. Such tests are unable to measure workers' on-the-job performance and can fail to distinguish between legal and illegal substances. Drug tests do not prevent accidents because they do not address the root problems that lead to substance abuse. Hair tests and urinalysis are inaccurate and produce thousands of "false positive" tests each year. Hundreds of thousands of American citizens are having their livelihoods jeopardized by a test that is of dubious accuracy at best. In addition, lower courts have struck down as unconstitutional the random testing of police officers, teachers and firefighters. Because drug tests detect workers' past drug use instead of impaired performance, such tests do not ensure a safe or drug-free workplace and encourage a false sense of security in employers and supervisors.