When the police believe a driver was impaired by both alcohol and drugs, California can charge a combined DUI under Vehicle Code 23152(g). These polysubstance cases are more complex than a straight alcohol DUI, and that complexity often works in the defense's favor. I am Joel Brand, and here is how I approach them.
What the prosecution has to prove
The prosecution must prove that the combination of substances actually impaired the driver to the point of being unable to drive with the caution of a sober person. A modest alcohol level that would not support an alcohol DUI on its own is often paired with a claim that drugs pushed the driver over the line. That theory depends on connecting specific drug evidence to actual impairment at the time of driving, which is a great deal harder than simply reading a breath number. The state has to show not just exposure to two substances but a genuine combined effect on driving.
Why there is no number to rely on
Unlike the 0.08 percent standard for alcohol, there is no legal limit for most drugs, so a combined case turns on proof of impairment rather than a clean threshold. The presence of a drug in the blood shows past exposure, not present impairment, and for many drugs, marijuana being the clearest example, the detection window stretches far beyond any actual effect. A person can test positive long after the drug stopped affecting them. That gap between detection and impairment is one of the central weaknesses in any drug or combined DUI prosecution.
The Drug Recognition Expert evaluation
Combined cases often rest on a Drug Recognition Expert, or DRE, evaluation, a twelve-step protocol an officer uses to opine that drugs contributed to impairment. The DRE process is structured, but it is far from infallible. It depends on subjective observations, it can be administered incorrectly, and its conclusions are an officer's opinion, not a laboratory result. I scrutinize whether the protocol was actually followed step by step, whether the officer was properly certified and current, and whether the physical findings the DRE relied on have innocent explanations like fatigue, nerves, or a medical condition.
Why these cases have weaknesses
Pairing a low alcohol reading with a weak drug-impairment theory creates real room to challenge the case. The two halves can be attacked separately: the alcohol level may be too low to mean much, and the drug evidence may show only exposure rather than effect. The prosecution's argument often depends on the inference that two substances together must have impaired the driver, but that inference has to be backed by actual evidence of impaired driving, not just the fact that both were present. Holding the state to genuine proof on the combined effect frequently exposes how thin the theory is.
Prescription and lawful use
Using a prescription or a legal substance is not a crime; driving while actually impaired is what the statute reaches. Many combined cases involve a prescribed medication taken as directed alongside a small amount of alcohol. The lawful use of the medication is not itself an offense, and the real questions are whether the driver was genuinely affected and whether the medication and alcohol actually interacted to impair driving. A patient following doctor's orders is in a very different position than the prosecution's narrative often suggests. See how prescription drugs affect a DUI defense.
The timing and testing problems
Combined cases inherit all the timing problems of an ordinary DUI and add their own. Blood is usually drawn well after driving, so it may not reflect the levels behind the wheel, and the interaction effects the prosecution alleges are difficult to pin to the moment of driving. Blood testing also has its own vulnerabilities, the qualifications of the person who drew it, the preservatives in the vial, the storage conditions, and the chain of custody, all of which apply with full force when the sample is the foundation of a drug case. Any break in that chain undermines the very evidence the combined theory depends on.
How I defend a combined DUI
I treat the alcohol and the drug allegations as two separate problems and attack each on its own terms, then challenge the assumption that they must have combined to impair driving. I examine the DRE evaluation closely, test the chain of custody and the blood analysis, account for any lawful prescription use, and hold the prosecution to proof of actual impairment at the time of driving rather than mere presence of substances. Combined DUI cases rise and fall on proof of impairment, which gives a prepared defense room to work. See also marijuana and drug DUI and my top DUI defenses.
Why prosecutors reach for the combined charge
It helps to understand why a combined charge appears in the first place. Often the alcohol level alone is too low to guarantee a conviction, perhaps below or near the limit, so the prosecution adds a drug theory to shore up a weak alcohol case. In other words, the combined charge is frequently a sign that neither half is strong on its own. Recognizing that changes the whole posture of the defense: rather than facing one solid case, you are usually facing two weak ones the prosecution hopes will add up to a conviction. Pulling them apart and exposing the weakness in each is exactly how these cases are won.
Sentencing and treatment considerations
Where a combined DUI cannot be defeated outright, the involvement of a prescribed medication or a substance-use issue can actually support a more favorable, treatment-oriented resolution. Courts respond well to a client who takes genuine steps to address the underlying issue, and documenting lawful prescription use, medical guidance, and any treatment can both undercut the criminal theory and improve the sentencing outcome. I weave that mitigation into the case from the start, so that even the fallback position is stronger than what the prosecution's opening offer would suggest.
Charged with a drug and alcohol DUI?
Every combined case turns on the specific substances, levels, and testing, which is exactly what I review with you. Use the free case analysis on this page, or call me directly at (888) 271-6644. I answer my own phone, 24/7.
Related: drug possession (HS 11350).