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Smoking Under the Influence

by Debra A. Newby


DEAR READERS: Do you have a legal question on your mind? If so, please email me. Your name will remain confidential. This Q & A Legal Column is intended as a community service to discuss general legal principles and does not create an attorney-client relationship.

Dear Debra:

Now that California has passed the recreational use of marijuana, I’m curious…will I get busted for driving while high? 

Signed: Stoned and Scared

Dear Not-S & S:

Good question. I think it is fair to say we are all trying to absorb the impacts of the recent election, both from the presidential race, as well as the ballot initiatives that passed, including Proposition 64, which legalized possession and sales of marijuana for recreational use.  

First, you must realize that even though Prop. 64 passed, an entire other set of laws apply to the operation of a motor vehicle…and rightly so. After all, if you are out-and-about behind the wheel of a 4,000-8,000 pound motor vehicle, you have a duty to operate that vehicle with utmost care. That is why California’s DUI Law, codified in CA Vehicle Code section 23152(e) makes it a crime to operate a vehicle under the influence of any alcoholic beverage or drug, including marijuana. The prosecuting attorney must of course show that the substance impaired the driver’s ability to drive. You should also know that California has adopted an implied consent standard, meaning that any person who drives a motor vehicle in our Golden State is deemed to have given their consent to a blood test, if lawfully arrested for a DUI.

So, the technical answer is “yes”, you may get busted for driving high if you are impaired. But, it gets really tricky when one analyzes the reality. For example, most of us know that if you have been drinking and driving, and your blood test is over 0.08%, you are in trouble. Yet, when it comes to cannabis, no similar baseline measure applies. In other states that allow recreational marijuana, like Colorado and Washington, you can be charged and convicted with a DUI if you are found with 5 nanograms of active THC per millimeter of blood. Although California has no specific impairment level for cannabis, the arresting officer can and will rely on other factors to determine whether you are impaired, such as your performance on field tests, your driving pattern and conduct, statements, and the presence of odor and drugs in your car. 

Some observers argue that testing for cannabis levels is unreliable, because THC (delta-9-tetrahydrocannabinol, for my science-driven readers) is fat-soluble and can remain in the driver’s system for hours or even days. If the driver is a chronic cannabis user, then the THC can remain for 2-30 days, depending on what study you read. Lab testing methods include a blood test, urine test (less reliable), and saliva swab test. Given the challenges with testing for cannabis, Prop 64 also earmarked something like $15 million over five years to the Highway Patrol to determine “protocols and best practices” for determining if the driver is under the influence. 

Your question prompts another one in my mind…does smoking MJ impair the ability to drive? The answer to that is rather cloudy, as politics, economic interests, and science twirl about in a Tasmanian-devil-style tornado, each trying to put their forces in play. On one end if the spectrum are folks like NORML, which infers that cannabis is safe and does not impair driving. They even proclaim that the auto fatality rate is unaffected by increased marijuana use, and that stoned drivers are a lot safer than drunk ones (  

Yet, a report from Colorado based Rocky Mountain High Intensity Drug Trafficking Area, concluded that pot-related fatalities spiked by 32% in 2014, the year Colorado opened retail stores selling cannabis. Also, a report by the American Automobile Foundation for Traffic Safety concluded that 10% of Washington drivers involved in fatal crashes between 2010 and 2014 had marijuana in their system. 

We still have much work to do. So many unknowns. For now, perhaps the best course is to be kind and attentive, not only on the highway, but with each other.

Debra A. Newby is a resident of Monte Rio and has practiced law for 34 years. She is a member of the California, Texas and Sonoma County Bar Associations and currently maintains an active law office in Santa Rosa which emphasizes personal injury law (bicycle/motorcycle/motor vehicle accidents, dog bites, trip and falls, etc.) and expungements (clearing criminal records). Debra can be reached via email (, phone (707-526-7200), or fax (526-7202).