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Washington's Per Se Marijuana Limit Debunked in Recent Article!

Posted by Nathan Webb | May 13, 2016 | 0 Comments

I have always stated that the Washington State Marijuana DUI Per Se limit is baseless and does not have an iota of analysis to back it up. The per se limit in Washington state is 5 ng/mL of whole blood of active THC. That means if you are caught driving after smoking marijuana and have a blood level of 5 ng/mL of whole blood you are automatically (per se) guilty of DUI.

Recently a study was completed basing the results of some DREs (Drug Recognition Exams) and their correlation to blood draws when THC was used. The researchers concluded, " Based on this analysis, a quantitative threshold for per se laws for THC following cannabis use cannot be scientifically supported." Basically the research shows the per se limit in Washington of 5ng/mL of whole blood is baseless or as they say, "it went up in smoke."

One interesting note was that in this study, on the walk and turn test (one of the standardized tests used to assist officers in making an arrest decision) 55.5% of the people who had not smoked at all passed it while only 6% of the marijuana smokers did, those that were drug free. (Note: this means the 44.5% of sober people couldn't pass the walk and turn). When the researchers compared the results to the various levels of THC found in the blood of those individuals who did smoke, there was no correlation to people with lower or higher THC levels doing better or worse. Essentially they determined the roadside tests are superfluous when making a determination as to the impairment of someone suspected of smoking or ingesting marijuana and driving.

You can read the article here for further information.

Call us today if you have been arrested for a DUI in Washington State. (425) 522-4200.

About the Author

Nathan Webb

Nathan "Nate" Webb has been repeatedly recognized by Washington Law and Politics Magazine as a Super Lawyer Rising Star, named one of Seattle's Top Attorneys by Seattle Met Magazine and is rated Superb (perfect 10 out of 10) by


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