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Marijuana DUI Standard in Washington

A Washington DUI is a serious offense for which penalties are severe. With the legalization of medicinal and recreational marijuana, police are arresting more and more drivers who test positive for THC levels in their blood. Yes, you can receive a DUI in Washington for driving while high, even if you do not appear to be impaired. Should you ever find yourself in this situation, you should consult with an expert DUI attorney promptly.

Washington’s DUI Standard for Marijuana Use

Similar to how there is a nationwide legal limit for alcohol, the state of Washington has its own limit for how much THC– the active ingredient in marijuana — can be in your system at any time while driving. The THC concentration may not exceed 4 nanograms per milliliter of blood. So, if you have 5 nanograms or more per milliliter of blood, you are automatically “guilty” of DUI in the eyes of law enforcement and the court as per Washington statute 46.61.502.

There are dissenters on both sides of the debate, with some claiming the limit is too high while others believe it is too low. Dr. Marilyn Huestis of the National Institute on Drug Abuse suggested that the standard is too high to capture impaired drivers after conducting a study on marijuana use and psychomotor function. She believes it is too low because THC concentration quickly diminishes within 24 hours below that 5 nanogram limit. Some people are impaired at a lower concentration.

On the other side, many active marijuana users understand the way tolerance works. Our bodies grow accustomed to substances differently. Many users of marijuana claim that as their tolerance builds up they may have 5 nanograms or higher THC concentration but be completely alert and not impaired behind the wheel. A measure of 5 nanograms/ milliliter of blood is controversial because of how differently marijuana users process the THC. Particularly for medical marijuana users who have a high tolerance for the drug and need it for medical issues, the limit seems unfair to some.

Currently, there is no scientifically accurate way to measure just how “high” or impaired someone is while using marijuana. Some users may abstain from the drug for days, get behind the wheel, and still contain a measurable amount of THC in their systems.

Penalties for a Washington DUI

A first conviction for DUI in the Evergreen State is a fine of $350 to $5000, a 24-hour to 1 year stay in jail (either one, or both); and a 90-day license suspension. Fines, jail time, and license suspension periods only increase the more convictions you have. If you have been arrested for DUI in Tacoma, contact The Law Offices of Daniel J. Murphy, Jr. for competent and aggressive representation.

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33515 10th Place South, #17
Federal Way, WA 98063



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506 S. 11th St.
Tacoma, WA 98402



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  • Criminal Defense
  • Auto Accidents
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Murphy’s Law Offices
506 S. 11th St.
Tacoma, WA 98402
Phone: (253) 312-6122

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