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How Cannabis Legalization Has Impacted Impaired Driving in Washington State

You've likely heard that regulating cannabis markets will lead to more stoned drivers on the road. Although the evidence in support of this claim is weak, it's repeated time and time again. So we thought we would ask members of law enforcement from Washington State what they think of this claim.
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Road to Hurricane Ridge, Olympic National Park, WA
Oksana Perkins via Getty Images
Road to Hurricane Ridge, Olympic National Park, WA

By: Nazlee Maghsoudi

You've likely heard that regulating cannabis markets will lead to more stoned drivers on the road. Although the evidence in support of this claim is weak, it's repeated time and time again. So we thought we would ask members of law enforcement from Washington State, where cannabis markets were legalized and regulated under Initiative 502 in November 2012, what they think of this claim.

In this interview, Sheriff John Urquhart of King County, and John Schochet, Deputy City Attorney for Policy and Constituent Affairs from the Seattle City Attorney's Office, share how they think regulation has impacted impaired driving.

A claim we often hear is that cannabis regulation will lead to greater impaired driving. What has your experience of cannabis impaired driving been since legalizing and regulating cannabis markets in Washington State?

Sheriff John Urquhart: The Washington State Patrol's numbers indicate that, despite the legalization of recreational marijuana, driving under the influence (DUI) has not measurably increased. My experience as Sheriff, and the experience of my officers, reflects this. Some people drove impaired on marijuana before legalization, and about the same number will do so after legalization.

John Schochet: Anecdotally, I do think you are getting more people driving under the influence of marijuana. Cannabis legalization does not seem to have increased DUIs overall, though it might be that some cannabis DUIs are substituting for alcohol DUIs. Overall, DUI increases are not an enormous problem when it comes to marijuana legalization, but it could be if left unchecked.

How has Initiative 502 impacted the way individuals are convicted of driving under the influence of cannabis?

Schochet: First, it's worth emphasizing that cannabis legalization didn't mean that impaired driving was legalized. What it did do was make it easier to convict people who are actually driving stoned, rather than those who simply show evidence of cannabis use in their blood.

There are two substances that can be determined by a blood test: Carboxy-THC and active THC. Carboxy THC doesn't indicate impairment because it stays in your blood for a long time. It just shows that you used cannabis at some point. Active THC actually shows impairment.

Without other evidence of impairment, basing conviction on carboxy alone is unreasonable. But before 502, a lot of people were being convicted of driving under the influence of cannabis based on just carboxy in the blood. Initiative 502 created an objective standard for determining cannabis impairment of 5 nanograms of active THC per milliliter of whole blood (ng/ml). So this objective standard created under regulation is a significant improvement compared to what a lot of prosecutors were using before.

Urquhart: Investigating impairment solely for marijuana use has historically been a little tricky. The officer would have to prove impairment based on his or her observations of the driver, and often a drug recognition expert would have to observe the driver as well. With the new per se limits on THC, however, it has become much easier to investigate and prosecute a driver for being impaired solely from marijuana.

So you have better guidelines for detecting cannabis impairment. How is that panning out in implementation?

Schochet: There are challenges, particularly because you need a blood test to accurately determine cannabis impairment, and you need it quickly. Why? Because you can't trace back how impaired someone was when they were driving based on the active THC in their blood two hours after they drove.

Getting blood is tricky because we can't suspend your license if you refuse to take a blood test (like we can if someone refuses to take a breath test), and because in Washington State you need a warrant to forcibly take someone's blood.

These problems aside, you can also convict someone by subjectively proving, beyond a reasonable doubt, that the person was under the influence of cannabis while driving. So, we are working on getting more police trained to identify marijuana intoxication. As more get trained, we are able to more effectively enforce the laws around cannabis impaired driving.

Beyond greater police training to detect it, is there anything else we can do to better address cannabis impaired driving?

Schochet: Public education is key. We've spent the last several decades educating people about the dangers of driving drunk and this has been, overall, a very successful effort.

Unfortunately, we are not there yet with marijuana. A lot of heavy users actually believe that it is fine to drive stoned. Maybe it is not as dangerous as alcohol or dangerous in the same way as alcohol, but our view of the evidence is that driving stoned is a problem. This education piece - effectively informing people that although cannabis is safe enough to be legal, it is not safe to drive under the influence of cannabis - is tricky.

A television commercial aired by the Washington Traffic Safety Commission as part of the 'Drive High Get A DUI' campaign.

Given all your experience, how do you respond to the claim that we shouldn't legalize and regulate cannabis because it will lead to more stoned drivers?

Schochet: Is there a concern with impaired driving? Absolutely. It's a huge issue with alcohol and has been for a long time. But our response isn't to ban alcohol. Our response is to go after people who drive impaired and to engage in public safety campaigns. So when it comes to impaired driving, I view it as something we should be worried about, but it is not a justification for banning marijuana.

Urquhart: The truth of the matter is that regulation will come with harms. The key is weighing the costs and benefits of a regulated vs. unregulated market. We have been fighting a futile drug war for over 40 years. I'm pleased we are not allowing the fear of change to impede the search for a better way.

The responses have been condensed for clarity.


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