PULLMAN, Wash. — Recreational marijuana was legalized in Washington state four years ago and lawmakers and law enforcement are still in search for the best ways to detect and deter drivers under the influence of the drug.
Marijuana DUI enforcement is tricky because chemically, THC is much different than narcotics like opioids or alcohol. As of now, the legal limit to drive is 5 nanograms per milliliter. This level is determined by a blood test. However, because THC is fat soluble, presence in the blood does not mean that marijuana was recently consumed.
Researchers said there is still a lot that is not confirmed about levels of THC and the resulting impairment behind the wheel.
“The 5 nanograms per mil was established when simply having presence of marijuana in your system was illegal,” WSU Assistant Professor of Chemistry, Dr. Brian Clowers, said. “What it means to be impaired is a different question. We don’t have enough scientific evidence using modern weed that people smoke to really kind of assess some of those things.”
Dr. Clowers and his colleagues conducted a research project at the beginning of the summer to look into marijuana impairment and develop a better way for law enforcement to test in the field. For the test, participants would bring their own weed, smoke it and then go through field sobriety testing with law enforcement while WSU researchers used field THC detectors.
“The goal long term has been to identify something that’s very similar to an alcohol breathalyzer, but because chemically alcohol–ethanol, specifically–is so much different than THC, the amount of THC that is on breath is vanishingly small,” Dr. Clowers said.
The subject of marijuana DUI research is caught in a couple different cross hairs. First, it is legal at the