One thing that confuses almost everyone I meet after a DUI arrest is why their paperwork lists two charges that sound like the same thing. I am Joel Brand, and I defend DUI cases throughout California. Most alcohol DUI cases are charged under two separate subsections of the same law, and they are not redundant. They are two different theories of guilt, and understanding the difference tells you a great deal about where the weaknesses in your case actually are.
One arrest, two charges
When you are arrested for a standard alcohol DUI, the prosecutor typically files two counts. The first is under Vehicle Code 23152(a), and the second is under Vehicle Code 23152(b). They arise from the same incident, the same stop, the same night. But they ask the jury to decide two different questions, and that is the whole point of charging both. The state wants two paths to a conviction so that if one fails, the other might still stand.
Count one: driving under the influence
The first count, Vehicle Code 23152(a), is about impairment. It says it is illegal to drive while under the influence of alcohol, meaning your physical or mental abilities were impaired to the point that you could not drive with the caution of a sober person. Notice what is missing from that definition. There is no number. You can be convicted under this subsection even if your BAC was below 0.08, if the prosecutor can convince a jury you were genuinely impaired. By the same token, the absence of a clean number does not save you here.
Count two: the 0.08 per se law
The second count, Vehicle Code 23152(b), is the per se law. Per se is Latin for in itself. This subsection makes it illegal to drive with a BAC of 0.08 or more, full stop. The prosecutor does not have to prove you drove badly or seemed drunk. The number alone is the offense. This is the cleaner charge for the state when the chemical test is high, because it sidesteps the messy question of whether you were actually impaired.
Why charging both matters to your defense
Because the two counts ask different questions, they have different vulnerabilities. The per se count lives or dies on the chemical test. If the breath or blood result can be challenged, on calibration, timing, mouth alcohol, or a rising blood alcohol argument, the 0.08 count weakens. The impairment count lives or dies on the officer's observations, the field sobriety tests, the driving pattern, and any innocent explanation for how you looked. A strong attack on the number does not automatically defeat the impairment count, and a strong attack on the officer's observations does not automatically defeat the number. I lay out the full menu in my guide to the top DUI defenses.
What conviction looks like on both
If you are convicted of both counts, you are generally only punished once. California does not stack the penalties for the (a) and (b) counts arising from a single act of driving, so people sometimes plead to one and have the other dismissed as part of a resolution. The practical sentence for a first offense looks the same either way, which is why the strategy is usually about which count, if any, is the most defensible, not about avoiding double punishment.
Drug DUIs work differently
This two-count structure is built for alcohol. When the allegation involves drugs, there is no equivalent per se number, because California has not set a legal threshold for THC or most other substances the way it has for alcohol. A marijuana DUI under Vehicle Code 23152(f) is charged purely on impairment, which makes the officer's observations and the drug recognition evaluation the entire battleground. I explain the broader category in my post on the difference between DUI and DWI in California.
How this opens the door to a reduction
Understanding that the case has two distinct pillars is also why DUIs so often resolve as something less than a DUI. When one pillar is shaky, the leverage that creates can move a case toward a wet reckless or another reduced charge. You can get a quick read on whether that is realistic for your situation with my wet reckless calculator, and I write about what drives that outcome in the post on what a prosecutor considers in a wet reckless plea.
What this looks like in a real case
Picture a stop where the breath result is 0.09, just over the line, but the driving was fine and the officer's report is thin on actual impairment. The per se count is the state's strong card, so the whole defense points at the number, the calibration history, the observation period, and the timing of the last drink. Now picture the opposite, a refusal case with no chemical number at all. There the state has to win on impairment alone, and every clue the officer claims to have seen, every line in the report, becomes the battleground. Same statute, two completely different fights, decided by which count the evidence actually supports.
Do not assume the higher number settles it
People with a high reading often assume the case is hopeless and the people with a borderline number assume they will walk. Both assumptions are wrong as often as they are right. A high number can come from a flawed machine, a contaminated sample, or mouth alcohol, and a borderline number can still support an impairment conviction if the officer's observations are strong. The charge structure is the reason a DUI is rarely as simple as the number suggests in either direction.
The bottom line
Your DUI is almost certainly two charges, not one, and they are not the same accusation written twice. One is about a number and one is about your behavior, and they fail for different reasons. A real defense starts by figuring out which pillar is weaker and pressing there. If you want that analysis for your own case, get a free written case analysis below, or call me directly at (888) 271-6644. I answer my own phone, 24/7. You can also read more from the DUI blog.