Driving Under the Influence of Marijuana in California

Legalization is not a pass to drive stoned

By Judy Malmon, J.D. | Reviewed by Canaan Suitt, J.D. | Last updated on June 26, 2023

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The legalization of cannabis in California has made the use of marijuana more common. But, as with alcohol, its legality does not make it acceptable or safe to operate a motor vehicle while impaired.

That said, impairment from marijuana can be a pretty tricky thing to assess accurately, efficiently, or even-handedly. While the influence of alcohol can be measured by blood alcohol content (BAC) using a breath test, blood test, or other chemical tests, there is no breathalyzer for tetrahydrocannabinol (THC), the intoxicant in marijuana. Even if there was, the drug’s effects can vary on different marijuana users.

Under California law, there is no “per se” rule for impairment due to drugs similar to the 0.08 percent BAC in the case of alcohol. The law simply states that “it is unlawful for a person who is under the influence of any drug to drive a vehicle.” Consequently, a citing law enforcement officer must assess the actual impairment of a driver.

Circumstances Leading to a Marijuana DUI

There are any number of circumstances under which a driver may come to be suspected of impaired due to marijuana, including:

  • A traffic stop for a moving violation;
  • A stop at a DUI checkpoint; or
  • A stop for a vehicle-related issue, such as a broken taillight.

In any of these circumstances, a police officer may come to suspect the driver is under the influence from smelling or seeing pot or paraphernalia in the car, or from observing the driving patterns or appearance of the driver. Any of these can be considered evidence of impairment.

Testing for the Presence of Marijuana

A citing officer may request assistance from an officer trained as a Drug Recognition Expert (DRE) to further assess a driver’s state. A DRE is trained to perform field sobriety tests and examine for specific signs of drug-related impairment. The written contemporaneous observations of a DRE can be used as evidence to support a drug-related DUI charge.

If arrested, the driver will be given a blood test to determine THC levels in their system. Under California’s implied consent law, you may not refuse to submit to being tested. Although, if you have a health-related reason why you can’t undergo a blood test, you may submit a urine test. These test results will also be used as evidence in a DUI arrest.

Disputing Presented Evidence

Because the presence of THC remains in your blood for as much as two days after smoking or consuming (and even longer in your urine), and there is no consensus as to what quantity would constitute impairment, the findings of a blood test don’t conclusively show that a driver was under the influence of the drug at the time they were driving.

If you’re arrested for a marijuana DUI case, having a reputable and experienced DUI defense attorney assist you in challenging the evidence of impairment can make a huge difference to the outcome of your case. An attorney can raise challenges as to:

  • The conclusiveness of any test-related data
  • The manner in which the test itself was conducted and its results handled
  • The appropriateness of the traffic stop
  • Other procedural issues related to your arrest and the evidence presented

Penalties for a DUI conviction for cannabis are the same as a DUI for alcohol. If it’s your first DUI offense, you may:

  • Be fined $390;
  • Face a six-month driver’s license suspension;
  • Face up to six months of jail time; or
  • Have to take three months of DUI school.

For subsequent convictions, your penalties increase to over a year of prison time, and fines up to $5,000. 

Get Legal Help from a California DUI Attorney

If you’re facing DUI drug charges, consult a criminal defense attorney with experience in DUIs as soon as possible. A DUI lawyer will understand marijuana DUI laws and defenses, and many lawyers provide free consultations. Search the Super Lawyers directory to find an experienced DUI attorney in your area.

If you’d like more general information about this area of the law, see our DUI/DWI law overview.

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