The Effect of Marijuana Use on Car Accident Liability

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Since the legalization of marijuana in Washington in 2012, there has been a significant increase in the number of drivers testing positive, often in combination with alcohol as well. These drivers pose a specific threat to others on the roads and if they are in a car accident, their marijuana use can be evidence against them.

Is there a "legal limit" for marijuana?

Washington State's Liquor and Cannabis Board (WSLCB) defines a legal maximum limit for “delta-9” THC levels at five nanograms per milliliter of blood (5 ng/mL). These levels serve to mark the baseline for driving under the influence (DUI) charges.

Under RCW 46.61.502, the state can charge an adult with DUI if:

  • The driver has a THC concentration of five or higher in his blood within 2 hours of driving.
  • The driver is under the influence of the drug alone or in combination with alcohol or other drugs.


Also under that statute, evidence of the blood level of anyone with a THC level greater than 0.00 may be used as evidence of a driver's being under the influence of or affected by marijuana usage.

“Green DUI” as Evidence of Negligence

Much like drunk driving, you can use driving under the influence of marijuana (sometimes referred to as a “green DUI”) as evidence of the other driver's negligence.

Every driver on the road has a duty to the other drivers and persons on the road to drive sober to preserve the safety of all. If a driver chooses to operate their vehicle under the influence of any substance that can impair their perceptions, reaction times, or processing speed, they are endangering not only themselves and their passengers but also others on the roads.

Negligence is a failure to uphold that duty to care. If another driver were to get into an accident with that impaired driver, she might be able to bring an action against that person for her injuries. The victim would need to prove:

  1. The driver under the influence had a duty of care (as all drivers do).
  2. The driver failed to uphold that duty by driving under the influence of marijuana (or any other mind-altering substance).
  3. The accident occurred because of the other party’s negligence.
  4. The claimant suffered injuries because of the accident and suffered damages.


If you or someone you love suffered injuries in an accident caused by an operator under the influence of marijuana, reach out to the car accident attorneys at Max Meyers Law PLLC. Contact us today at 425-399-7000 for legal advice and counsel.

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Max is a Kirkland personal injury attorney handling cases in Seattle, King County & surrounding in WA State.