California has been a leader in progressive cannabis policy for decades. As one of the first states to legalize cannabis both for medicinal and recreational use by adults, California has had to implement laws to protect the public. These have included laws against driving after consuming cannabis.
Unfortunately, impaired driving after using cannabis is a real safety concern, in part because it can be so difficult for police to prove. Drivers impaired by cannabis could cause crashes that hurt others, but limits to cannabis-related medical science mean that police could arrest and prosecute innocent people for drugged driving.
How do officers establish impairment?
There are no reliable roadside tests at this time
The unfortunate truth for police officers attempting to enforce sober driving laws, there are very few reliable ways to conclusively establish cannabis impairment at the wheel. Testing someone for THC or the metabolic byproducts of breaking down the active ingredients in cannabis usually will not work, as people can test positive for weeks after the last time they used cannabis.
Failing a test, in other words, is not an indicator of impairment. Field sobriety tests are similarly unreliable for detecting cannabis impairment, and the few devices touted as cannabis breathalyzers have so far proven unreliable or too expensive to mass-produce and use for enforcement purposes.
Officers rely on a combination of self-reported information and their interpretation of people’s behavior to validate that someone was under the influence. They may also perform chemical tests to help bolster the evidence they have for their case, although such tests may not hold up under close scrutiny by the courts.
Understanding how the state establishes cannabis impairments and the difficulty in doing so could help you if you face drugged driving charges in California.