False positives also can be caused by glitches in the testing technology. 5 Today, the most conservative estimates of the number of false positives per year run into the thousands. Considering the number of times workers are tested, as many as 1 in every 15 workers can expect to have a false positive at some point in his or her career. Hundreds of thousands of American citizens are having their livelihoods jeopardized by a test that is of dubious accuracy at best. Random drug testing does not ensure a drug-free workplace.
Employers have the right to want a safe and productive workplace.
Randomly administered drug tests, however, do nothing to further this goal and can actually hinder it. Overlooked in the debate about drug testing is the fact that drug testing has never been scientifically shown to improve workplace safety or productivity. This is most likely because drug tests do not measure current impairment. They can only determine whether metabolites from past drug use are present in the medium being tested. For instance, metabolites from marijuana consumption can be detected in the urine for more than 30 days after the person's last exposure to marijuana.