For drunk driving, the .08 blood-alcohol standard for intoxication has been adopted in every state. For drugged driving, however, the question of what constitutes illegal impairment depends on the state and on the substance.
In about a dozen states, drugged driving is defined as using a certain amount of a drug that appears on an official list of prohibited substances. In the majority of states, however, drugged driving is defined more broadly, based on observations of law enforcement officers.
What about Washington state? In this post, we will address that question.
Marijuana and THC
In Washington the issue of marijuana-impaired driving began to receive considerable attention even before voters approved Initiative 502 to legalize recreational cannabis use in 2012. There was even a term coined for this: green DUI.
Initiative 502 set a specified amount of THC (the psychoactive compound in marijuana) that a driver can have in his or her system. If you have 5 or more nanograms of THC in your system, and officers had probable cause to stop you, you can be charged with drugged driving - even if you aren't exhibiting any effects.
Let's keep in mind, however, the importance of probable cause. Having a THC of 5 more nanograms does not necessarily mean that officers had probable cause to stop you in the first place. Under our constitution, law enforcement officers don't have open-ended authority to make traffic stops, absent erratic driving or some other valid reason to pull you over.
That said, if there truly was probable cause, having 5 or more nanograms of THC in your system while driving makes it a per se drugged driving violation.
Effects of impairment
There are also many other possible drugged driving scenarios besides a THC of 5 nanograms or more. One is a combination of alcohol and marijuana consumption. Another is the use of other drugs, such as heroin or a painkiller such as oxycodone.
Prescription drugs, in particular, are very common these days. New synthetic drugs that mimic the qualities of more established drugs are also increasingly available.
And of course there could also be a combination of alcohol and these other drugs. Under Washington law, the question is whether someone "exhibited effects" that reflect impairment of driving ability.
Washington relies on the observations of law enforcement officers to recognize the effects of these drugs. In theory, these officers can identify the visible effects of impairment after someone has consumed restricted substances.
In practice, however, there is no bright line that allows officers to easily identity impairment from drugs. If you have been charged with drugged driving, you can push back against the charges with the help of a skilled defense attorney.