Lawmakers in Pennsylvania approved the use of marijuana for medical use in 2016, and more than 250,000 people in the state have since registered to use the drug to treat conditions ranging from chronic pain to anxiety. However, every one of Pennsylvania’s medical marijuana patients commits a crime each time they get behind the wheel because of the state’s zero tolerance standard. Under this standard, a driver can be convicted of DUI if any trace of a Schedule I drug or a metabolite of that drug is discovered in a blood test. Marijuana is still a Schedule I drug under federal law.
The zero tolerance standard is not supported by science
This is an especially thorny legal issue because THC, which is the cannabinoid that gives marijuana its psychoactive properties, can be detected in blood tests up to a month after the drug is consumed. For medical marijuana patients, simply venturing out onto the roads at any time could lead to their arrest. Advocacy groups and experts critical of the zero tolerance standard say that metabolites do not impair drivers and measuring THC levels is not considered by scientists to be a reliable method of determining impairment.
The standard is being challenged in court
Pennsylvania’s zero tolerance standard is being challenged by a medical marijuana patient who was charged with driving while under the influence on Feb. 25 when a blood test revealed her blood THC concentration to be 8.1 nanograms per milliliter. Her attorney plans to argue that drivers who take prescription opioids are only charged with DUI in Pennsylvania if they are clearly impaired, and he will also point out that states including Arizona and Michigan no longer allow THC metabolite evidence to be introduced in DUI cases.
Expert witnesses in DUI cases
The effectiveness of these arguments will likely hinge on the credibility of the expert witnesses the attorney will call to testify. Juries tend to find testimony from respected experts extremely compelling, and experienced criminal defense attorneys may call on biologists, chemists or psychologists when the charges against their clients are based on scientific principles that the drafters of the laws in question likely did not fully understand.