Recreational marijuana may be legal for adults in California, but driving while impaired by cannabis remains illegal. Unlike alcohol DUI cases, however, there is no .08% equivalent that automatically establishes a marijuana DUI based solely on the amount of THC detected in a driver’s system.
If you have been arrested for driving under the influence of marijuana in Fresno, the prosecution must establish more than the fact that you used cannabis at some point. The evidence must support the allegation that you were under the influence while driving.
Fresno DUI attorney Gregory W. Fox has more than 20 years of criminal defense experience and represents clients facing marijuana DUI, drug DUI, and other driving-under-the-influence charges throughout Fresno and Central California.
Call (559) 222-5800 to request a consultation.
Is It Illegal to Drive After Using Marijuana in California?
California law prohibits driving while under the influence of any drug, including marijuana.
The fact that recreational cannabis is legal for adults in California does not make it legal to drive while impaired. The same is true when marijuana is used for medical purposes.
But using marijuana and driving under the influence of marijuana are not necessarily the same thing.
In a marijuana DUI case, one of the central questions is whether the prosecution can establish that cannabis actually impaired the driver’s ability to operate a vehicle safely at the time of driving.
For a broader overview of California DUI law, see our guide to California DUI laws, BAC limits, and penalties.
Is There a Legal THC Limit for Driving in California?
California does not currently have a THC concentration that functions like the .08% blood alcohol concentration limit used in alcohol DUI cases.
That distinction is important.
In an alcohol case, a BAC of .08% or higher can provide the basis for a per-se DUI charge. Marijuana cases do not work the same way.
A blood test may detect THC or cannabis-related compounds, but the presence of THC does not by itself answer the most important question in the case: Was the driver actually impaired at the time he or she was driving?
As a result, marijuana DUI prosecutions may depend heavily on the totality of the evidence rather than a single chemical-test number.
How Do Prosecutors Try to Prove a Marijuana DUI?
Because there is no .08% equivalent for marijuana, prosecutors may rely on several different types of evidence to try to establish impairment.
Evidence may include:
- The driver’s observed driving pattern
- The reason for the traffic stop
- Statements made by the driver
- Physical observations made by law enforcement
- Field sobriety test performance
- Blood or other chemical-test results
- The presence of marijuana or cannabis products in the vehicle
- Observations concerning the odor of marijuana
- Testimony from the arresting officer
- Evaluation by a Drug Recognition Expert or Evaluator
- Evidence concerning when marijuana was allegedly consumed
Each piece of evidence should be examined individually and in context.
An officer’s conclusion that a driver appeared impaired does not relieve the prosecution of its burden to prove the charge.
THC Blood Tests and Marijuana DUI
Chemical testing can play an important role in a marijuana DUI investigation, but interpreting a THC blood result is different from interpreting a BAC result in an alcohol case.
Cannabis compounds can remain detectable after the intoxicating effects associated with marijuana use have diminished.
That means the presence of THC or its metabolites may provide evidence of marijuana use without necessarily establishing the degree of impairment at the time the person was driving.
Factors that may affect the significance of a test result include:
- When marijuana was consumed
- The amount consumed
- The method of consumption
- The potency of the cannabis product
- The driver’s frequency of marijuana use
- The amount of time between driving and the blood draw
- How the sample was collected, stored, and analyzed
The defense should therefore consider both the laboratory result and the circumstances surrounding the test rather than treating the mere detection of THC as proof of impairment.
Marijuana DUI and Field Sobriety Tests
Law enforcement officers investigating a suspected drug DUI may ask a driver to perform field sobriety tests.
Officers may use the driver’s performance as evidence supporting an arrest.
Field sobriety test performance, however, can potentially be affected by factors other than marijuana impairment, including:
- Fatigue
- Anxiety or nervousness
- Medical conditions
- Physical injuries
- Footwear
- Uneven surfaces
- Lighting or weather conditions
- The instructions given by the officer
- The manner in which the tests were administered
Body-worn camera or patrol-vehicle video may provide important evidence concerning both the driver’s behavior and how the field sobriety tests were conducted.
What Is a Drug Recognition Expert?
Some marijuana DUI investigations involve an officer trained as a Drug Recognition Expert or Drug Recognition Evaluator, commonly referred to as a DRE.
A DRE may conduct an evaluation and offer an opinion about whether a driver appears to be impaired by a particular category of drugs.
The prosecution may rely on that evaluation along with chemical-test results, observations by other officers, driving behavior, and additional evidence.
A DRE opinion is still evidence that can be examined and challenged.
The defense may review what the evaluator observed, whether the evaluation was conducted properly, whether alternative explanations exist for the reported signs and symptoms, and whether the conclusions are consistent with the remaining evidence.
What if I Have a Medical Marijuana Recommendation?
Lawful or medically authorized marijuana use does not provide a defense to driving while actually impaired.
At the same time, lawful use does not automatically establish that a person was impaired while driving.
The relevant question in a DUI case is not simply whether the driver was legally entitled to possess or use cannabis. The issue is whether the prosecution can prove that the driver was under the influence at the time of driving.
This distinction can be especially important when chemical testing detects cannabis compounds in someone who uses marijuana regularly.
Can You Be Charged With DUI for Prescription or Other Drugs?
Yes. California’s drug DUI laws are not limited to marijuana or illegal drugs.
A person may potentially be charged with driving under the influence involving:
- Prescription medications
- Over-the-counter medications
- Marijuana or cannabis products
- Illegal controlled substances
- A combination of different drugs
- A combination of alcohol and drugs
Having a valid prescription does not necessarily prevent a DUI charge if prosecutors allege that the medication impaired the person’s ability to drive safely.
Conversely, merely establishing that a person had a particular substance in his or her system does not necessarily establish impairment.
Marijuana and Alcohol DUI
Some DUI investigations involve allegations that the driver consumed both marijuana and alcohol.
California law prohibits driving while under the combined influence of alcohol and drugs.
These cases may involve both BAC evidence and evidence of cannabis use.
The defense should examine what each type of evidence actually establishes, including whether the prosecution can prove that the combination of substances impaired the driver’s ability to operate the vehicle safely.
Learn more about alcohol-related and drug-related DUI charges on our Fresno DUI attorney page.
Can a Marijuana DUI Affect Your Driver’s License?
Yes. A drug DUI conviction can result in driver’s license consequences.
The DMV process in a drug-only DUI case, however, may differ from a traditional alcohol DUI case.
For example, a drug-only DUI without an alcohol-related BAC allegation does not necessarily trigger the same immediate Administrative Per Se suspension based solely on a chemical-test result that commonly occurs after an alcohol DUI arrest.
A driver’s license may still be suspended or revoked following a drug DUI conviction, and other circumstances—including a chemical-test refusal or allegations involving alcohol in addition to drugs—can create separate DMV issues.
Because the driver’s license consequences depend on the particular allegations and evidence, the arrest paperwork and DMV notices should be reviewed carefully.
What Happens if You Refuse a Chemical Test?
A chemical-test refusal can create consequences separate from the underlying marijuana DUI allegation.
After a lawful DUI arrest, California’s implied-consent laws may require a driver to submit to chemical testing. Refusing or failing to complete a required test can result in driver’s license suspension or revocation.
Whether a legally sufficient refusal occurred can depend upon the circumstances.
The defense may examine:
- Whether the arrest was lawful
- What test was requested
- What the driver was told about refusing
- Whether the driver actually refused
- Whether the driver attempted to comply
- Whether required procedures were followed
If you received a notice of suspension or revocation, pay close attention to the deadline for requesting a DMV hearing.
Defenses to a Marijuana DUI Charge
The appropriate defense depends on the circumstances and evidence in the individual case.
Potential issues may include:
The Traffic Stop Was Unlawful
Law enforcement generally needs a lawful basis to stop or detain a vehicle.
The defense can examine the officer’s stated reason for the stop and whether the circumstances legally justified the detention.
The THC Evidence Does Not Establish Impairment
A chemical test showing cannabis use does not necessarily establish when marijuana was consumed or the degree to which the driver was impaired at the time of driving.
The timing and interpretation of chemical testing may therefore become important.
The Driver’s Behavior Had Another Explanation
Fatigue, anxiety, medical conditions, physical limitations, allergies, environmental conditions, or other factors may potentially explain observations that an officer attributed to drug impairment.
Field Sobriety Testing Was Unreliable
The defense may examine how tests were explained and administered, the conditions under which they were performed, and whether video evidence supports the officer’s description of the driver’s performance.
The DRE Evaluation Can Be Challenged
The conclusions of a Drug Recognition Expert are not automatically conclusive.
The defense can compare the evaluator’s conclusions with body-camera footage, chemical testing, medical information, witness testimony, and other available evidence.
The Blood Test or Laboratory Evidence Is Questionable
Blood evidence may raise issues involving collection, handling, storage, laboratory procedures, chain of custody, or interpretation.
The significance of a particular THC result should be evaluated in the context of the entire case.
The Prosecution Cannot Prove Driving
In some cases—particularly accidents or situations where police arrive after the vehicle has stopped—the prosecution may need to establish who was actually driving.
Being near or inside a vehicle does not necessarily prove that a particular person drove while impaired.
What Should You Do After a Marijuana DUI Arrest?
If you have been arrested for marijuana or drug DUI in Fresno, several steps can help protect your ability to evaluate and defend the case:
- Keep all paperwork provided by law enforcement. Court and DMV documents may contain important deadlines.
- Write down what you remember. The timing of marijuana use, the traffic stop, officer questioning, field sobriety tests, and chemical testing may later become important.
- Preserve potentially relevant evidence. Receipts, text messages, photographs, video, location information, and witness information may be useful.
- Avoid discussing the case publicly or on social media. Statements about when or how much marijuana you used could potentially become evidence.
- Have an attorney review the evidence. Marijuana DUI cases can involve very different scientific and evidentiary issues from alcohol DUI prosecutions.
Frequently Asked Questions About Marijuana DUI in California
Can you get a DUI for marijuana in California?
Yes. California prohibits driving while under the influence of marijuana or another drug when it impairs the driver’s ability to operate a vehicle safely.
The fact that recreational marijuana is legal in California does not make impaired driving legal.
What is the legal THC limit for driving in California?
California does not currently use a specific THC concentration as the equivalent of the .08% BAC limit for alcohol.
As a result, marijuana DUI cases generally require an evaluation of the overall evidence concerning impairment rather than relying exclusively on a particular THC number.
Does testing positive for THC prove a marijuana DUI?
Not by itself.
A positive test can be evidence that marijuana was used, but the significance of the result depends on the circumstances. The prosecution must still establish the elements of the DUI offense, including that the driver was under the influence at the relevant time.
Can I get a DUI if I legally purchased the marijuana?
Yes. Legal possession or use of marijuana does not authorize driving while impaired.
The same general principle applies to prescription medication: lawful use does not prevent a DUI charge if the drug actually impairs the person’s ability to drive safely.
Can I get a marijuana DUI if I have a medical recommendation?
Yes. Medical authorization does not provide a legal right to drive while impaired.
However, having used marijuana for medical purposes also does not automatically prove that you were impaired when you drove.
Can marijuana DUI charges be reduced or dismissed?
The outcome depends upon the facts and evidence.
Issues involving the traffic stop, chemical testing, DRE evaluation, field sobriety tests, officer observations, proof of driving, constitutional violations, or the prosecution’s ability to establish impairment may affect how a case is resolved.
No particular result can be guaranteed.
Can a marijuana DUI be expunged?
Some qualifying California DUI convictions may later be eligible for dismissal under California’s record-clearing laws.
Eligibility depends upon the conviction, sentence, completion of probation or other requirements, and the individual’s circumstances.
Learn more about California expungement and post-conviction relief.
Speak With a Fresno Marijuana DUI Attorney
Marijuana DUI cases present different scientific and evidentiary questions from traditional alcohol DUI prosecutions. A positive THC test does not eliminate the need to examine whether the prosecution can actually prove impairment at the time of driving.
Gregory W. Fox has more than 20 years of criminal defense experience and personally handles the cases accepted by the Law Office of Gregory W. Fox. He represents clients facing marijuana DUI, drug DUI, and other driving-under-the-influence charges throughout Fresno and Central California.
If you have been arrested or are facing charges for driving under the influence of marijuana or another drug, contact the Law Office of Gregory W. Fox to discuss your case.
Call (559) 222-5800 to request a consultation.