Here is a fact the prosecution would rather you not dwell on: the crime is driving with a BAC of 0.08% or more while you were driving, not when the test was taken 30 to 90 minutes later at the station. The rising BAC defense lives in that gap. I am Joel Brand, and for the right case it is one of the most effective challenges to a breath or blood number.
The science of absorption
Alcohol is not in your blood the instant you drink it. It has to pass from your stomach and small intestine into your bloodstream, a process that takes time. So your BAC rises for a stretch after your last drink, reaches a peak, and only then begins to fall. Depending on what and when you ate, how much you drank, and your own physiology, that peak can arrive anywhere from roughly 30 minutes to two hours after your last drink. If you were still in that rising phase when you were stopped, your BAC behind the wheel could have been under 0.08% even though the later test, taken after your level kept climbing, read higher.
Why the delay between driving and testing matters
There is almost always a gap between when you were driving and when the evidentiary test was administered. The officer has to make the stop, conduct the investigation, run the field sobriety tests, make the arrest, and transport you to a station or have a blood draw done. Thirty minutes to well over an hour is typical. During that entire interval, your body chemistry kept changing. The test captures your BAC at the moment of testing, not the moment of driving, and the law only criminalizes the latter. The longer the delay, the more room there is to argue your driving-time BAC was lower.
When it applies
The defense is strongest when your result is close to the limit, your last drink was fairly close to the time of driving, and the test was taken well after the stop. Example: a 0.09% blood draw an hour after driving may mean you were at 0.07% behind the wheel. That difference is the whole case under Vehicle Code 23152(b), and it also undercuts the impairment theory under 23152(a). The closer the number is to 0.08%, the more powerful this argument becomes.
The "last drink" timing is everything
This defense turns on the timeline, so the details of your last drink matter enormously. If you finished your final drink shortly before driving, there is a strong chance the alcohol had not fully absorbed when you were behind the wheel, meaning your true driving BAC was still climbing toward the number the machine later recorded. That is why I take a careful history: what you drank, how much, over what period, when you stopped, when you were stopped by police, and when the test was finally administered. Each of those data points helps reconstruct where on the curve you actually were while driving.
Food, body chemistry, and individual variation
Absorption is not uniform. Drinking on an empty stomach speeds it up; a full meal slows it down and can delay the peak significantly. Body weight, sex, metabolism, and even the type of drink all affect the curve. Because of this variation, no one can simply assume your BAC was the same when you drove as when you were tested. That uncertainty cuts in your favor, because the prosecution bears the burden of proving your BAC while driving, and the rising curve introduces genuine reasonable doubt about that exact figure.
Retrograde extrapolation cuts both ways
Prosecutors sometimes try to use a technique called retrograde extrapolation to estimate backward from the test result to the time of driving, assuming you were already past your peak and declining. But that assumption only holds if you were in the elimination phase, and if you were actually still absorbing, the same math runs the other direction and supports the defense. I use forensic toxicology to show that the state's backward estimate rests on assumptions that do not fit the facts of your night.
A walkthrough of how it plays out
Picture a common scenario. You finish your last drink at a restaurant at 9:45 and leave a few minutes later. An officer stops you at 10:00 for a minor equipment issue, then spends 20 minutes on questions and field sobriety tests before arresting you. You are taken to the station and finally blow into the evidentiary machine at 10:55, more than an hour after your last drink. The reading is 0.09%. At 10:00, when you were actually driving, your body was still absorbing that last drink, and a toxicologist can credibly testify your BAC at the wheel was below 0.08%. The state's only number is from 55 minutes after you stopped driving, and it does not prove the element it has to prove.
Why this defense is so often overlooked
Many people, and even some lawyers, treat the chemical test number as the final word. It is not. The number is a snapshot taken at the station, and the law cares about a different moment entirely. Recognizing that distinction, and having the timeline and the science to exploit it, is what separates a careful defense from one that simply accepts the prosecution's framing. In close cases, this single argument is frequently what converts a likely conviction into a dismissal or a reduction to a lesser charge like a wet reckless.
How I build it
I work with the timeline (last drink, stop, and test), the testing records, and where needed a forensic toxicologist to map the curve and show where you likely were at the time of driving. It pairs naturally with attacks on the testing equipment and the mouth alcohol problem, and certain medical conditions affect absorption too. It is also a live issue at the DMV hearing. See my full top DUI defenses.
Think this applies to you? Let's find out.
Whether this defense fits depends on the specific records and facts of your stop, which is exactly what I review. Use the free case analysis on this page, or call me directly at (888) 271-6644. I answer my own phone, 24/7.
From the DUI blog: Does Drinking at a Private Party Before a DUI Stop Change Your Defense?.
From the DUI blog: Your Breathalyzer Number After a California DUI Arrest: What That Reading Actually Means.
From the DUI blog: How Long Between Your DUI Stop and the Breathalyzer Actually Matters in California.