One of the provision of I-502 (Washington’s Marijuana decriminalization statute) was to make it illegal to drive with more than 5 nanograms of THC in your blood. Officers face the problem of not really knowing if someone is impaired by THC. Marijuana is different than alcohol. Pretty much everyone can recognize when a person is impaired by alcohol, because of the odor, the slurred speak, the poor coordination.Marijuana DUI Arrest With THC, officers are trained to look for tremors, subtle changes in pupil dilation, and other factors. The Inlander magazine recently did an article about a Spokane police officer whose ability to predict the presence of 5 nanograms of marijuana was only slightly above 50%. The article sites a study by the Spokane Public Defender’s office documenting that the officer in question has requested 58 samples of blood after the subjects were arrested for DUI. 27 of those individuals arrested had no THC in their system at all or had THC in an amount less than 5 nanograms present.
This is consistent with what I have found in my practice as a defense lawyer. I can recall one case where a person was arrested for impaired driving, and the DRE swore that the defendant was high on marijuana. The officer went so far as to say that the suspect had a green tongue, and had burn marks on his lips from a hot pipe. When we received the toxicology tests 2 months later we learned that there was no THC (or carboxy THC) in the arrestee’s blood at all. Instead, the drug that was found was methadone.
Scientists at Washington State University are studying better ways for the police to test drivers for THC when the driver is detained at the side of the road. However, these tests will likely take years to develop and to be certified for use in the courts in Washington.