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Can You Get a DUI With a BAC below .08%?

Posted by Richard Wagner | Apr 28, 2024


dui lawyer california

Q: How likely is it to be convicted of a DUI when your blood alcohol content is below the legal limit?

Q: Can you still get a DUI with a BAC below 0.08%?

Benjamin F. Warlick got into a traffic accident, and California Highway Patrol Officer Chris Jensen came to investigate.

Mr. Warlick told the CHP officer he had been drinking alcohol earlier in the evening. The reading from a preliminary alcohol screening (PAS) test showed 0.07 percent at 12:17 a.m.

The prosecution charged Mr. Warlick with violating California Vehicle Code Section 23152(b), which says it is:

“unlawful for any person who has 0.08 percent or more, by weight, of alcohol in his or her blood to drive a vehicle.”

Warlick's DUI defense attorney made a motion to exclude any expert testimony based on retrograde extrapolation analysis.

At the pretrial hearing, Marisa Ochoa, an employee of the San Diego County Sheriff's Department, known as a criminalist, testified for the prosecution.

Q: How Can They Charge Him For Having a BAC over .08 if the Breathalyzer was .07?

A:  Ms. Ochoa testified that based on the .07 PAS test result, Mr. Warlick's statements about his drinking, and studies regarding normal alcohol elimination rates, Ms. Ochoa's opinion was that Mr. Warlick had a BAC of at least 0.08 percent at the time of driving.

Judge Edward P. Allard III ruled Ms. Ochoa's proposed testimony was inadmissible based on Baker v. Gourley (2002) 98 Cal.App.4th 1263. Judge Allard said, according to the Baker case, a violation of Section 23152(b) cannot be proved without a chemical test showing a blood-alcohol level of 0.08 percent or greater.

Based on the court's ruling, the prosecutor told the court that he could not prove a violation of Section 23152(b) without retrograde extrapolation evidence. (Retrograde extrapolation is calculating the BAC to a point back in time. It is used to estimate the level at the time you were driving based on a test result that was taken later.)

To answer the questions above, no matter what the results of your breath or blood tests are, you can count on the prosecution to bring in a witness who will testify that your BAC at the time you were driving was higher compared to the results of the tests.

The trial court dismissed the charge. The prosecution appealed.

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The Appellate Division of the Superior Court in San Diego disagreed with the trial court. It said that Baker v. Gourley did “not stand for nearly so sweeping a proposition.” It further said, “The Baker decision is limited by its terms to the “so-called ‘ Admin Per Se" laws where the … [DMV] suspends a driver's license…”  Read more about DMV Admin Per Se Hearings

In distinguishing Baker, the Appellate Division also noted,

“the factual context of that case is of crucial importance in understanding the scope of the holding. Baker's statement precluding reliance on circumstantial evidence was based expressly on the lack of a “valid chemical test. Here, in contrast, there was a perfectly valid chemical test—that happened to show a blood-alcohol level of only 0.07 percent.”

The court's characterization of the PAS test as a "valid chemical test" is puzzling.

Vehicle Code Section 13388 says “a preliminary alcohol screening test device is an instrument designed and used to measure the presence of alcohol in a person based on a breath sample.”

Vehicle Code Section 23612(h) says, “A preliminary alcohol screening test that indicates the presence or concentration of alcohol based on a breath sample in order to establish reasonable cause to believe the person was driving a vehicle in violation of ... is a field sobriety test and may be used by an officer as a further investigative tool.”

Vehicle Code Section 23612 (a) (1) says a chemical test comes after arrest: “A person who drives... is deemed to have given his or her consent to chemical testing of his or her blood or breath for the purpose of determining the alcoholic content of his or her blood, if lawfully arrested for an offense... in violation of Section 23152 …”

Despite the above vehicle code statutes, the Appellate Division reversed the trial court.

It reinstated the Section 23152(b) charge and denied the request to exclude the retrograde extrapolation testimony.

The citation for this opinion is People v. Warlick (2006) 162 Cal. App. 4th Supp. 1.


"Among the many reasons for the infeasibility of retrograde extrapolation, three stand out: 1) lack of knowledge… about the time of the alcohol concentration peak and absorption-postabsorption status, 2) ignorance about the mathematical characteristics and mean rate of change of the individual's blood or breath alcohol elimination curve, and 3) unpredictable irregularities of the curve, especially short term fluctuations from the best-fit trend line of the blood or breath alcohol curve.”1

“...No forensically valid forward or backward extrapolation of blood or breath alcohol concentrations is ordinarily possible in a given subject and occasion solely on the basis of time and individual analysis results.”2

“The status of ethanol absorption is an important consideration when attempts are made to estimate (BEC) blood ethanol concentration at the time of the offense from the blood ethanol concentration determined at time of sampling. This technique is called back tracking BEC, or retrograde extrapolation, and is a dubious practice.”3

If you've been arrested for a DUI, contact The Law Office of Richard Wagner at (714) 721-4423.


1 Dubowski, K.M., “Absorption, Distribution, and Elimination of Alcohol: Highway Safety Aspects," Journal of Studies on Alcohol Supplement No. 10: 103, July 1985.

2 Dubowski, K.M., “Absorption, Distribution, and Elimination of Alcohol: Highway Safety Aspects," Journal of Studies on Alcohol Supplement No. 10: 106, July 1985.

3 Jones, A.W., Jonsson, K.A., and Neri, A., "Peak Blood-Ethanol Concentration and the Time of Its Occurrence After Rapid Drinking on an Empty Stomach” Journal of Forensic Sciences, Vol. 36. No. 2: 376-377, March 1991.

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Richard Wagner

Attorney Profile Defense Lawyer Richard Wagner upholds and defends freedoms and liberties enshrined in our United States and California Constitutions.  “Richard was able to achieve an even better outcome for my case than what we initially thought was possible. I couldn't be more grateful to h...