Hair follicle testing and false positives for marijuana

Drug testing is sometimes ordered by Wisconsin courts handling child custody cases where a parent is suspected of illegal drug use. The hair follicle test is designed to detect metabolites produced in a person’s body after use of illegal or prescription drugs. A new study in Germany has found, however, that this can be a problem for marijuana testing.

The hair follicle drug test looks for cannabinoids in a test subject’s hair strands to detect marijuana use. Cannabinoids can be transferred to a non-smoker via contact with a marijuana smoker or secondhand smoke, researchers found. This could result in a false positive for marijuana.

Urine tests are the most commonly performed type of drug test, but hair follicle testing is often preferred for child custody cases because it allows lab analysts to look for drug use over a longer period of time. Urine tests are considered the standard for employment screening. Marijuana stays in a person’s system for longer than other drugs, which creates another problem with drug tests. A person could test positive for marijuana on a hair follicle test months after using the drug.

A false positive test could have devastating consequences for parents who are fighting for custody. After failing a drug test, many courts will order supervised contact only and in some cases, no visitation rights at all. Some parents could even face termination of their parental rights if they fail a drug test.

A parent who is concerned about drug testing in a child custody case may wish to consult with a family law attorney. Legal counsel may argue that certain tests are unreliable while asserting to the court that denying parental rights to the client would not be in the best interests of the child.