A recent published study, presented by Freiburg University in Germany, has found that rolling a joint is enough to make you fail a drug test. Even indirect contact with cannabis can give you a false positive, with bug implications for legal cases that revolve around a drug test as evidence.
Researchers chose 10 participants to roll one joint on five consecutive days, and urine tested them to make sure they didn't smoke before or during the study. By the fifth day, and the fifth joint, most of the participants had detectable levels of THC and THCA in their hair. Even four weeks after their first exposure hair tests still showed both THCA and decarboxylated THC.
Those who have had to submit to drug tests know all too well about THC's habit of lingering in the body for long periods of time. This study proves you don't even need to get high to show up positive; the act of breaking up bud exposes your skin to enough THC to show up on a drug test.
This finding isn't all bad, it proves that analytical findings may be wrongly interpreted as a proof of consumption, because THC can be transferred by close bodily contact. An employer may not have to listen to your excuses, but a court of law may now have a hard time proving someone smoked pot beyond a reasonable doubt solely based on a positive drug test. Since direct and even indirect contact with cannabis can lead to a false positive, lawyers may have an easier time getting toxicology findings thrown out as evidence.
A previous study has shown that Δ9 -tetrahydrocannabinolic acid A (THCA-A), the non-psychoactive precursor of Δ9 -tetrahydrocannabinol (THC) in the cannabis plant does not get incorporated in relevant amounts into the hair through the bloodstream after repeated oral intake. However, THCA-A can be measured in forensic hair samples in concentrations often exceeding the detected THC concentrations. To investigate whether the handling of cannabis plant material prior to consumption is a contributing factor for THC-positive hair results and also the source for THCA-A findings in hair, a study comprising ten participants was conducted. In this study, the participants rolled a marijuana joint on five consecutive days and hair samples of each participant were obtained. Urine samples were taken to exclude cannabis consumption prior to and during the study.
THCA-A and THC could be detected in the hair samples from all participants taken at the end of the exposure period (concentration range:
15-1800 pg/mg for THCA-A and < 10-93 pg/mg for THC). Four weeks after the first exposure, THCA-A could still be detected in the hair samples of nine participants (concentration range: 4-57 pg/mg). Furthermore, THC could be detected in the hair samples of five participants (concentration range: < 10-17 pg/mg).
Based on these results, it can be concluded that at least parts of the THC as well as the major part of THCA-A found in routine hair analysis derives from external contamination caused by direct transfer through contaminated fingers. This finding is of particular interest in interpreting THC-positive hair results of children or partners of cannabis users, where such a transfer can occur due to close body contact. Analytical findings may be wrongly interpreted as a proof of consumption or at least passive exposure to cannabis smoke. Such misinterpretation could lead to severe consequences for the people concerned. Copyright © 2015 John Wiley & Sons, Ltd.
Refferences:
High Times magazine
US national Library of Medicine