Residents of Washington who consume alcohol or marijuana more than likely are keenly aware of the legal limits for both substances above which driving is illegal. For alcohol, people can be arrested for driving under the influence if their blood alcohol level is above .08. And they can also be slapped with a DUI if they have more than 5 nanograms of THC in their system while they are behind the wheel.
So in theory, there's no way that Mustaf Ahmed should have been convicted of DUI in the state. His measured blood alcohol level was .073, so he wasn't "drunk." And because authorities only found 3.4 ng of THC in his blood, he was not legally "impaired" by marijuana either.
Here's why: a provision in Washington DUI law states that an individual is legally impaired if he or she is driving:
While the person is under the combined influence of or affected by intoxicating liquor, marijuana, and any drug.
The prosecutors argued that the combined effects of the alcohol and marijuana in Ahmed's system were enough to warrant a charge of DUI, and the jury agreed. Ahmed's appeal was based on the fact that the jury did not specify that he was convicted based on the abovementioned provision of the law. But the appeals court disagreed, noting that the jury didn't need to make such a distinction.
Moral of the story: even if you smoke a little weed and drink a little booze before driving, you still might get busted for DUI in Washington.