How Do Marijuana DUI Blood Tests Work in Washington?

If you drive in the state of Washington, you are treated as having consented to a breath test once you are lawfully arrested for DUI. If you refuse, you can lose your license. However, there is no breath test for a marijuana DUI. When officers suspect marijuana impairment, the chemical test they rely on is usually a blood test.

The initial steps of a marijuana DUI stop may look similar to an alcohol-related DUI, but the way officers investigate and how the State uses the results is different. Blood results can drive both the criminal charge and a separate license suspension. Marijuana DUI blood test results can significantly affect the outcome of your case. The Tacoma marijuana DUI lawyers at Smith & White can review the evidence in your case and develop a strong defense strategy for you.

What to Expect in a Marijuana DUI Blood Test

Whether you submitted to testing and the State claims you were high, you refused testing, or the officer obtained a search warrant for your blood, the Department of Licensing (DOL) can still move to suspend or revoke your license. That license action is separate from any criminal charge.

You have the right to ask for a hearing to challenge DOL’s action. The deadline is short and measured in days, not weeks, so it is important to act quickly. If your request is timely and you present a strong defense, you may be able to overturn the decision. In many cases, your attorney can appear for you at the hearing and challenge the legality of the stop, the arrest, the warnings you received, and the way the test was requested.

In general, refusing a chemical test usually brings more severe consequences than taking the test and failing it. A refusal can trigger a longer suspension and may be used as evidence against you in the criminal case.

How Officers Build a Marijuana DUI Case

To pull you over for a marijuana DUI, the police officer must have a reasonable suspicion of criminal wrongdoing or a traffic violation. A reasonable suspicion is more than a hunch. The officer must be able to explain specific observations to the court.

Once the officer detains you, they begin investigating and looking for probable cause to arrest you for a marijuana DUI. They may ask questions, watch how you move, and look inside the vehicle. Signs of possible marijuana impairment include:

• The odor of marijuana in the car or on your clothing

• The presence of a pipe, joint, or other marijuana paraphernalia

• Bloodshot or glassy eyes

• Irregular, slow, or confused speech

• Other physical signs that suggest you are high

Officers may ask you to perform field sobriety tests or call in a drug-recognition-trained officer if one is available. Those observations, combined with what they see and smell, form the basis for a decision to arrest. If the officer believes they have probable cause, they may arrest you and move to the testing stage.

How Marijuana Blood Tests and Warrants Work

After arrest, you will likely be asked to submit to a chemical test. For marijuana, the most common and reliable chemical test is a blood test. A blood test can show whether you have THC (tetrahydrocannabinol) in your system and, if so, the measured concentration.

A blood test cannot show whether you smoked, vaped, or ate marijuana. It also cannot say exactly when you used. In Washington, if you are at least 21 years old, you can be charged with a marijuana DUI if a valid test shows five nanograms per milliliter of blood (5 ng/mL) or more of active THC within two hours of driving. For drivers under 21, any amount of THC above 0.00 can support a “minor DUI” style charge, even when the level is under 5 ng/mL.

If you refuse to take the blood test, law enforcement officers may ask a judge for a search warrant to draw your blood. Judges often review warrant applications by phone or electronically. Once the warrant is obtained, officers transport you to a hospital or clinic so a qualified professional can draw your blood. The blood sample is then sealed and sent to a toxicology lab for testing.

You can be convicted of a marijuana DUI based on the results of a blood test. However, the 5 ng/mL limit does not always match real-world impairment. THC can linger in the body because it is stored in fat and released slowly over time. The amount of time between driving and the blood draw, your tolerance, and your pattern of use can all affect what that single number really means. A defense attorney can look at those details and, when appropriate, challenge whether the lab result truly proves impairment.

Warrants, Exigent Circumstances, and License Consequences

In many cases, officers seek a warrant before drawing blood. No warrant is necessary if you validly waive the warrant requirement or if true exigent circumstances exist, such as certain serious collisions or medical emergencies where delay would risk loss of evidence or public safety.

Blood drawn for the purpose of determining marijuana levels is considered lawful under RCW 46.20.308 if an officer has reasonable grounds to believe that you were driving or in physical control of a vehicle while under the influence or in violation of RCW 46.61.503. When the State claims that those conditions were met, they will try to use that blood result both in court and in the DOL hearing.

If a test is administered that shows your THC concentration is above 0.00 and you are under age 21, or if a lawful test shows a per se level of THC for an adult driver, or you refuse to submit to a test, the arresting officer or the Department can serve notice of its intention to deny, revoke, or suspend your driver’s license, privilege, or permit to drive.

You must receive written notice of your right to a hearing. That notice should explain the steps you need to take and the deadline for requesting a hearing. In many cases the notice arrives by mail, which makes it easy to overlook. Because driving on a suspended or revoked license is also a crime, it is important to watch for that notice, act quickly, and work with an experienced attorney to try to avoid a suspension or revocation. In some situations, your lawyer can also help you explore options like an ignition interlock license so you can keep driving to work or school if a suspension goes into effect.

Consult Our Attorneys After a Marijuana DUI Stop

If you are arrested for a marijuana DUI and a blood test was taken—or you refused a test—you can ask the attorneys at The Law Offices of Smith & White, PLLC, to explain what the results may mean and what your options are. We can review the stop, the warrant or consent process, the lab report, and your DOL paperwork to see where the State’s case is weak and what deadlines you face.

We represent people in the Tacoma area and throughout Pierce, King, Kitsap, and Thurston Counties. Contact us at (253) 203-1645 or through our online form.