The concentration of THC, the ingredient in marijuana which causes the high, in one’s blood sample is a key to determining whether one is charged with what I will refer to as “marijuana DUI”. One may not operate a vehicle with a THC level of 5.00 or higher within two hours after driving under the new marijuana DUI law. See RCW 46.61.502. However for those who possess a CDL and drive a commercial vehicle, any measurable concentration of THC is a basis to be charged with marijuana DUI. See RCW 46. 25.090. For minors, those under the age of 21, there is also a zero tolerance for THC within the blood sample which differs from the .02 BAC limit allowed for alcohol. See RCW 46.61.503.
Even without regard to THC concentration, one may still face a marijuana DUI charge if his or her driving is found to be affected by marijuana. This is similar to a DUI based on alcohol consumption where a person can be charged with DUI even if the BAC is below a .08 as long as there is sufficient evidence that the person’s driving was affected by alcohol. See RCW 46.61.502.
It is also important to point out that a DUI charge may arise not only from consumption of alcohol or marijuana, but from impairment to driving caused by any drug including legal drugs. It, for example, is not a defense to a DUI charge that one’s impaired driving was caused by an over-the-counter drug or prescription medication.
Washington State’s implied consent provision is also in sync with the new marijuana DUI law. Implied consent is an essential term of art under DUI law which is defined as consent that a driver implicitly provides to have a sample of his or her breath tested for alcohol or THC concentration if he or she is suspected of driving under the influence of alcohol or marijuana. See RCW 46.20.308. However, it is important to note that there is no implied consent for a blood draw which requires an officer to either obtain a search warrant or the driver’s express consent.
The penalties for marijuana DUI are pretty much the same as they are for a regular alcohol induced DUI. A marijuana DUI will be counted as a prior DUI should one subsequently commit another DUI offense regardless of whether it is based on alcohol or marijuana consumption.
Experts agree that the THC limit of 5.00 is only an arbitrary number to determine driving impairment. It is quite possible for impaired driving to occur at much lower THC levels. There is a nice Seattle Times article which discusses the questionable nature of the designated 5.00 THC level which may be accessed at http://www.seattlepi.com/local/article/Marijuana-research-Is-the-limit-for-4233733.php. At the same time, attempting to find any correlation between THC concentration in one’s blood and driving impairment may not be possible according to information provided by the National Highway Traffic Safety Administration (See http://www.nhtsa.gov/People/injury/research/job185drugs/cannabis.htm).
There is no doubt that smoking marijuana will impact one’s driving. However, similar to the arguments that I have presented in previous blog posts about the subjective nature of accusing someone of driving under the influence of alcohol, determining whether one is driving under the influence of marijuana is even more difficult to assess. Now that the Washington State legislature has come up with this arbitrary 5.00 THC limit for defining when driving impairment is caused by marijuana, DUI law deviates that much more from the reality of what really constitutes driving under the influence of anything.