Marijuana DUI Laws in Washington State

As of December 1, 2012, people in the state of Washington are allowed to possess up to 1oz of marijuana for personal use. In addition, the new law set a “per se,” or maximum, threshold THC level that drivers cannot exceed while driving.  As stated in the law, A person is guilty of driving while under the influence of intoxicating liquor, marijuana, or any drug if the person drives a vehicle within this state:

  1. And the person has, within two hours after driving, an alcohol concentration of 0.08 or higher as shown by analysis of the person’s breath or blood made under RCW46.61.506; or
  2. The person has, within two hours after driving, a THC concentration of 5.00 or higher as shown by analysis of the person’s blood made under RCW 46.61.506; or
  3. While the person is under the influence of or affected by intoxicating liquor, marijuana, or any drug; or
  4. While the person is under the combined influence of or affected by intoxicating liquor, marijuana, and any drug.

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What is Washingtons Legal Limit for Marijuana?

Before the passage of I-502 which legalized marijuana, Washington had a zero-tolerance policy regarding driving under the influence of marijuana’s active ingredient, delta-9 tetrahydrocannabinol (THC), which many believe impairs driving ability. Prior to the law’s effective date of December 1, 2013, any level of THC in a driver’s blood was prohibited. Furthermore, drivers under the age of 21 were prohibited from having any active THC in their blood. Now, drivers 21 or older are permitted a very low amount of the active THC in their blood—up to 5 ng (nanograms) per milliliter of blood. Driving under the influence of more than 5 ng per milliliter of blood is punishable by law.

There is much controversy over whether any particular driver will be impaired by 5 ng of delta-9 THC. Even the National Highway Traffic Safety Administration (NHTSA) has published materials that cast doubt upon the fairness of establishing a bright line “per se” level of impairment. In their 2004 publication Drugs and Human Performance Fact Sheets, the authors state that it is “difficult to establish a relationship between a person’s THC blood or plasma concentration and [driving] performance impairing effects. . . .concentrations of the parent drug [marijuana] and the metabolite [delta-9 THC] are very dependent on patterns of use as well as dose.” Thus, they conclude that “it is inadvisable to try and predict effects based on blood THC concentrations alone, and currently impossible to predict specific effects based on THC-COOH [inactive THC metabolite] concentrations.”

The reason for this is that people become tolerant to any drug, including THC, after time. Thus, an individual may have a seemingly high level of THC in their blood, but not be too impaired to drive. In fact, in 1983, NHTSA publishedMarijuana and Actual Driving Performance, where they concluded, “THC’s adverse effects on driving performance appear relatively small.”

Everyone reacts to marijuana differently. If the driver in question did not drive in an impaired manner, the jury can reject a prosecutor’s case and find the driver not guilty.

Under 5ng/ml and the “Affected By” Element of Marijuana DUI Laws

It is a common mistake to believe that if your breath or blood alcohol concentration (BAC) is under 0.08 percent, or below the new 5 ng/ml limit for THC, you cannot be convicted of a DUI. This is incorrect. The 0.08 and 5 ng/ml limits allow, but do not require, the jury to presume you are impaired at those levels or higher, regardless of whether the driver was actually impaired. But even when a driver is under those limits, they may still be convicted of a DUI under the “affected by” element if the prosecutor can prove that less than 5ng of THC caused the suspect’s ability to drive to be impaired to any appreciable degree. This means that if you are in an accident or are pulled over for driving erratically, you may still be convicted of a DUI while under the legal limits because the jury may conclude that even a negligible amount of THC impaired your driving.

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Marijuana DUI Defense in Washington State

Testing for Marijuana DUI: The Blood Draw

The twelfth step of the marijuana DUI evaluation is the blood test, which is optional. However, unlike the field sobriety tests and DRE evaluation, if you refuse to take the blood test, the Department of Licensing will revoke your driver’s license for at least one year. In addition, the prosecutor will likely try to use your refusal to take the blood test as evidence that you believed you were guilty, assuming that if you were innocent you would have freely submitted. There are many reasons why a person may not wish to submit to blood testing, including a fear of needles, hospitals, or of an inaccurate analysis. However, it usually does not benefit the driver to refuse the blood test, because even if the test is positive for marijuana, there are a multitude of things that can go wrong in the taking of the blood, in storing it, and in analyzing it. If there are serious problems in any part of this process, the analysis might not be permitted to be used against you in court.


Drawing Blood Without Your Consent

The blood draw is typically done at a hospital, medical clinic, or sometimes, in a medical aid car/ambulance. The blood draw may only be performed by a physician, registered nurse, licensed practical nurse, nursing assistant, physician assistant, first responder, emergency medical technician, health care assistant, or technician trained in withdrawing blood (phlebotomist). Currently, officers are not trained to draw blood, but in at least one state (Arizona) officers may draw blood from the driver and often do so while the driver is seated in the back of the patrol car!

Note that if you are in an accident and are unconscious, the officers have authority to take your blood without your permission under the law. This was established to ensure the officers have a way to collect evidence without having to wait for you regain consciousness in order to give permission, because the longer the officer waits, the less active the drug will be in your system.

Marijuana DUI: Blood Analysis

After blood is drawn, it is delivered to the Washington State Toxicology Laboratory (WSTL) for analysis. It usually takes a few months before the result is reported to the officer, who then reports it to the prosecutor (and DOL if alcohol is present above .08). This causes a delay between the date of the arrest and the filing of charges. That delay can take several weeks to months.

The method of analysis of the blood is “selected ion monitoring gas chromatography mass-spectrometry.” Ms. Callahan has extensive training in gas chromatography, having received advanced training at Axion Labs in Chicago. She understands that blood testing is subject to a multitude of errors in the analytical process, whereas most attorneys (judges and prosecutors included) believe that blood testing is the “gold standard” of alcohol/drug testing and is virtually unassailable. Nothing could be further from the truth. A lawyer trained in the science that underlies the analytical process knows what problems and errors to look for in reviewing the work of the State Toxicology Laboratory. It takes that level of knowledge to find the thread that will unravel the prosecution’s case. Only a few lawyers in Washington State have availed themselves of this critically important training, which is so necessary to defending a marijuana DUI.


If you have been arrested for a Marijuana DUI in Washington State, give us a call today. (206) 866-6739 or complete our online form below: