Can I Be Charged With DUI if I Was Using Prescription Drugs, Marijuana, or Other Drugs?

Yes. In California, you can be charged with DUI even if you did not drink alcohol and even if the drug you used was legal, prescribed, recommended by a doctor, or purchased from a licensed dispensary. A DUI is not limited to drunk driving. California law also prohibits driving while under the influence of any drug, or while under the combined influence of alcohol and drugs, when the substance affects your ability to drive safely.

This can surprise people who are arrested after taking medication exactly as directed, using marijuana lawfully, or combining a small amount of alcohol with a prescription or over-the-counter drug. However, the central question in a drug DUI case is not simply whether the substance was legal. The question is whether prosecutors can prove that, at the time you drove, the substance impaired your mental or physical abilities so that you could not operate a vehicle with the caution of a sober person using ordinary care under similar circumstances.

At the Law Office of Joshua R. Bourne in San Diego, attorney Joshua R. Bourne represents clients facing DUI and criminal charges throughout San Diego County. As a former San Diego prosecutor and experienced criminal defense lawyer, Mr. Bourne understands how the government builds these cases, where the evidence may be weak, and why drug DUI allegations often require careful investigation rather than quick assumptions.

California DUI Law Applies to Drugs, Not Just Alcohol

California Vehicle Code Section 23152 is the main misdemeanor DUI statute. Many people are familiar with California’s alcohol-related DUI laws, including the 0.08 percent blood alcohol concentration rule. Drug DUI cases are different.

Vehicle Code Section 23152(f) states that it is unlawful for a person who is under the influence of any drug to drive a vehicle. Vehicle Code Section 23152(g) states that it is unlawful for a person who is under the combined influence of any alcoholic beverage and drug to drive a vehicle.

These provisions can apply to many substances, including marijuana, prescription pain medication, sleeping pills, anti-anxiety medication, muscle relaxers, stimulants, certain antidepressants, seizure medication, allergy medication, and illegal controlled substances. They can also apply to over-the-counter medication if the prosecution claims the medication impaired your ability to drive.

The law does not require the drug to be illegal. It also does not automatically excuse a driver because the medication was prescribed. A valid prescription may be highly relevant to the defense, but it is not a complete defense by itself if prosecutors can prove actual impairment.

Prescription Drug DUI Charges in San Diego

Prescription drug DUI cases often begin with ordinary driving behavior. An officer may claim that a driver drifted within a lane, stopped too slowly, appeared drowsy, had slurred speech, gave delayed answers, or seemed confused during the stop. The driver may then explain that they recently took medication. What the driver views as an innocent explanation may become part of the officer’s DUI investigation.

Common medications that may appear in prescription drug DUI cases include opioid pain relievers, benzodiazepines, sleep aids, ADHD medication, muscle relaxants, and medications that warn against driving until the patient understands how the drug affects them. Even medications taken for legitimate health reasons can raise suspicion if the officer believes the driver’s balance, coordination, attention, reaction time, or judgment was affected.

However, these cases are not always straightforward. A person may look tired because of stress, illness, injury, diabetes, lack of sleep, anxiety, or the emotional impact of being stopped by police. A person may perform poorly on field sobriety tests because of age, weight, footwear, uneven pavement, weather, back pain, knee problems, or medical conditions. A blood test may show the presence of a medication, but the presence of a drug does not always prove impairment at the time of driving.

That distinction matters. In many prescription drug DUI cases, the defense must focus on whether the government can connect the medication level, the officer’s observations, and the driving behavior to actual impairment beyond a reasonable doubt.

Marijuana DUI Is Legalization’s Most Misunderstood Issue

California allows adult recreational marijuana use and medical marijuana use, but it remains illegal to drive while under the influence of marijuana. A driver can be arrested for DUI after smoking, vaping, eating edibles, using concentrates, or consuming other cannabis products if law enforcement believes the driver was impaired.

Unlike alcohol DUI cases, California does not have a simple “0.08 equivalent” for THC. There is no universal THC number that automatically proves marijuana impairment in the same way that 0.08 percent blood alcohol concentration can create a per se alcohol DUI charge. THC affects people differently, and THC can remain detectable after the strongest impairing effects have passed. This is one reason marijuana DUI cases often turn heavily on officer observations, toxicology, driving patterns, and the opinion of a Drug Recognition Expert.

Marijuana cases may also involve related allegations, such as possession of an open container or open package of cannabis in a vehicle. Health and Safety Code Section 11362.3 restricts possessing an open container or open package of cannabis or cannabis products while driving, operating, or riding in the passenger compartment of a vehicle. Vehicle Code Section 23222 also addresses possession of open containers of alcohol or marijuana while driving. These allegations are separate from DUI, but they may influence how an officer interprets the stop and whether prosecutors believe marijuana use occurred close in time to driving.

A marijuana DUI charge should not be treated as automatic proof of guilt. The defense may examine whether the officer confused lawful possession with impairment, whether the alleged symptoms were consistent with cannabis use, whether the blood draw was properly handled, and whether the prosecution can prove the driver was impaired when driving rather than merely having THC in their system.

DUI Involving Illegal Drugs or Controlled Substances

Drug DUI charges may also involve illegal drugs or controlled substances, including cocaine, methamphetamine, heroin, fentanyl, or other substances. These cases may lead to additional criminal charges depending on what police claim they found during the stop, search, or arrest. For example, a DUI arrest may turn into a case involving drug possession, possession of paraphernalia, probation violations, or other allegations.

Even when the alleged substance is illegal, prosecutors still must prove the elements of DUI. The government generally must show that the defendant drove and was under the influence of a drug at the time of driving. Evidence of possession or prior drug use is not the same thing as proof of impaired driving. The timing of use, the amount detected, the reliability of the test, and the officer’s observations all matter.

These cases can also raise search and seizure issues. Police must have a lawful basis for the traffic stop, the detention, the arrest, and any search. If law enforcement violated constitutional limits, key evidence may be challenged. That can be especially important when the case depends on drugs allegedly found in the car or statements made during a roadside investigation.

How Police Investigate Drug DUI Cases

A drug DUI investigation may include several stages. First, the officer looks for driving clues, such as weaving, speeding, delayed reactions, unsafe turns, or an accident. Next, the officer observes the driver’s appearance, speech, movements, odor, pupils, coordination, and answers to questions. The officer may request field sobriety tests and may ask whether the driver took any medication, smoked marijuana, or used drugs.

In some cases, a Drug Recognition Expert, often called a DRE, may be brought in to evaluate the driver. A DRE may look at pulse rate, pupil size, eye movement, muscle tone, balance, divided attention, and other physical signs. The officer may then form an opinion about whether the driver is under the influence of a category of drugs.

After a lawful DUI arrest, chemical testing becomes a major issue. Vehicle Code Section 23612 is California’s implied consent statute. For drug DUI arrests, the law provides that a person who drives in California is deemed to have consented to chemical testing of blood for the purpose of determining drug content if lawfully arrested for certain DUI offenses. If a blood test is unavailable, urine testing may apply. The statute also addresses situations where a person first chooses a breath test, but the officer has reasonable cause to believe a blood test will show drug impairment.

Refusing or failing to complete a required chemical test can create additional consequences, including license suspension or revocation periods and potential enhanced penalties if convicted. Refusal issues are technical, and the exact consequences depend on the facts, the advisements given, the person’s prior history, and whether the arrest was lawful.

Why Blood Test Results May Not Tell the Whole Story

Drug DUI cases often rely on toxicology, but blood test results are not always as clear as they look. A lab report may show that a drug or metabolite was detected. That does not always answer the most important legal question: was the person impaired when they drove?

Different drugs behave differently in the body. Some medications may remain detectable after therapeutic effects decline. THC can remain in the bloodstream or be detected in ways that do not neatly correspond to driving impairment. Some substances have active and inactive metabolites. The time between driving, arrest, blood draw, and testing can also matter.

There may also be issues with collection, storage, chain of custody, testing methods, lab interpretation, contamination, or reporting. In the right case, an attorney may review whether the blood draw was lawful, whether the sample was properly preserved, whether the testing method was reliable, and whether the prosecution’s interpretation goes further than the science supports.

Possible Penalties for a California Drug DUI

A drug DUI conviction under Vehicle Code Section 23152 can carry many of the same types of consequences as an alcohol DUI. For a first misdemeanor DUI conviction, Vehicle Code Section 23536 sets out potential jail time and fines. A conviction may also involve DUI education programs, probation, driver’s license consequences, court assessments, increased insurance costs, employment problems, professional licensing concerns, and a permanent criminal record unless later relief is available.

The consequences can become more serious if the person has prior DUI convictions, refused chemical testing, was involved in a crash, had a child in the vehicle, drove at high speeds, was on probation, or caused injury.

If another person is injured, prosecutors may consider Vehicle Code Section 23153, which covers DUI causing injury. That statute applies when a person drives under the influence and, while driving, commits an unlawful act or neglects a legal duty, proximately causing bodily injury to someone other than the driver. DUI with injury can be charged as a misdemeanor or felony depending on the circumstances, injuries, criminal history, and prosecutorial decision-making.

Because the consequences can reach far beyond the courtroom, it is important to take a drug DUI arrest seriously even if it is a first offense, even if the drug was prescribed, and even if you believe you were safe to drive.

Why Choose the Law Office of Joshua R. Bourne?

The Law Office of Joshua R. Bourne is located in downtown San Diego only blocks from the downtown courthouse. The firm represents clients throughout San Diego County in DUI and criminal defense matters.

Attorney Joshua R. Bourne founded the firm in 2006 after working as a Deputy City Attorney in San Diego and later gaining additional litigation experience. His background gives him insight into how prosecutors evaluate cases, what evidence they look for, and what weaknesses may affect their ability to prove guilt. The firm handles misdemeanor and felony cases, with an emphasis on DUI and domestic violence defense, and is known for taking a practical, level-headed approach to serious criminal allegations.

For clients facing a prescription drug, marijuana, or controlled substance DUI, that approach matters. These cases are often personal, stressful, and technical. You need a lawyer who will look beyond the label of the charge, review the evidence carefully, and develop a strategy based on the specific facts rather than assumptions about drug use.

Contact a San Diego Drug DUI Defense Attorney

If you were arrested or charged with DUI after using prescription medication, marijuana, or another drug, do not assume the case is hopeless. Legal use is not always a complete defense, but the prosecution still has the burden of proving impairment beyond a reasonable doubt. The evidence may be incomplete, exaggerated, scientifically weak, or open to challenge.

The Law Office of Joshua R. Bourne can review what happened, explain the charges, evaluate the police reports and chemical test evidence, and help you understand your options. Whether your case involves a first-time DUI, marijuana, prescription medication, alleged drug impairment, a refusal allegation, or an accident, early legal guidance can make a significant difference.

To discuss your case with an experienced San Diego DUI defense attorney, contact the Law Office of Joshua R. Bourne for a free consultation. Call to speak with the firm and learn how Joshua R. Bourne may be able to help protect your rights, your license, and your future.