California companies usually rely on urine tests for pre-employment drug screening, but more thorough employers sometimes call for hair follicle tests. Hair tests are considered to be the scientific gold standard for toxicology testing because they are virtually impossible to fool and can often detect drug use that took place several months earlier. However, recent research conducted in Germany indicates that hair follicle tests may not be as unimpeachable as was once believed.

Researchers from the Institute of Forensic Medicine in Germany say that hair follicle toxicology tests conducted on hair samples taken from individuals who have come into contact with marijuana users or marijuana smoke can test positive even when the drug has not been smoked or otherwise consumed by the subjects. The research also shows that the biogenetic precursor of the psychoactive compound THC was discovered in tests performed on hair from individuals who had merely handled marijuana.

The research is significant because marijuana is one of the most widely used illegal drugs in the United States and hair follicle tests are considered to be extremely reliable. Employers often accept the results of hair follicle tests without hesitation, and an inaccurate test could lead to an employee being fired unfairly, passed over for promotion unfairly or denied workers’ compensation benefits after a workplace accident. A leading pre-employment drug screening company say that they performed more than 200,000 hair follicle tests in 2014.

Federal and California laws provide legal protections and remedies for workers who have been harassed or discriminated against. Workers may also initiate litigation when they have been fired unfairly. An attorney with employment law experience could explain these legal protections and assess the merits of a discrimination, harassment or wrongful termination lawsuit.