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The Science of Marijuana DUI Law

Posted Tuesday, March 21, 2017 by Lizanne Padula.

alt textWhat’s the Legal Limit?

The media has done a good job of inflating the panic regarding marijuana DUIs in Washington State. This is a controversial subject because proving someone was under the influence of marijuana while driving is not as exact a science as proving someone had a BAC of .08%. Regardless of the scientific measures, driving under the influence of any drug or alcohol, marijuana included, is unlawful and can result in DUI charges and a conviction. Nevertheless, proving someone was driving while under the influence of marijuana is not as cut and dry as the media or authorities would have you believe. To better understand how someone is convicted of a marijuana DUI, let’s look at the science:

Washington law utilizes an impairment standard of 5.0 nanograms of THC per milliliter of blood within 2 hours of driving. This is called the per se limit. This standard has been fought on many sides because THC does not leave one’s blood as predictably or readily as alcohol does. And, for regular users, their blood THC level may not drop below an active THC level even if they did not recently consume marijuana. This means it is possible for someone to be convicted of driving under the influence even if he or she had not smoked or consumed THC for a lengthy period prior to driving. The 5.0 nanogram standard was even found to be unfounded by the AAA. There is also conflicting science on what a 5.0 nanogram translates into in terms of level of impairment. State toxicologists still have difficulty in attributing impairment to a particular THC blood level. Unfortunately, this is the legal standard in Washington.

A suspect might also undergo at 12-step evaluation by a drug recognition expert (DRE). The DRE will look for signs to attempt to classify what drug the driver may have consumed, including THC; in addition, the DRE will perform a protocol to make observations about the driver’s coordination, eyes, and even their vitals. The results of such an evaluation in conjunction with a lawful blood draw may be enough to convict the driver of DUI—even if his or her THC level is less than the 5.0 nanogram legal limit.

If you are facing DUI charges for driving under the influence of marijuana, speak with an attorney as soon as possible. A skilled Washington criminal defense attorney who has experience in DUI defense can advise you of your rights and help you defend them in court. You should not be unfairly convicted because of unfounded science, but you need to understand how the legal standard applies to your case. Having a knowledgeable criminal defense attorney assist you with your case and taking on both the science and the officer’s observations and conclusions that led to your arrest for DUI will give you the best chance of fighting your charges.

Have you been arrested for a DUI? The attorneys at Padula & Associates, LLC understand your concerns and can help you fight your charges and defend your rights. Our attorneys are experienced in DUI and criminal defense and can help you take on DUI allegations with confidence. For 10 years Padula & Associates has been serving those in King County, Snohomish County, and surrounding areas with aggressive criminal defense services for DUIs, domestic violence, and other criminal charges. Call us 24/7 at 425-883-3366, email us at or fill out our free consultation form today.