California Supreme Court: No Challenging of Breathalyzer Accuracy in DUI Cases


The California Supreme Court has held that general scientific evidence refuting the accuracy of all breathalyzers in California DUI cases is inadmissible as evidence. The decision, however, does not prohibit the introduction of evidence that a particular breathalyzer is malfunctioning.

The issue was brought before the California Supreme Court when the trial court in a California DUI case agreed with the prosecutor and excluded the testimony of a defense expert who testified that breathalyzers, in general, can be inaccurate.

California Highway Patrol had stopped Terry Vangelder for allegedly going 125 miles per hour on a San Diego Highway in 2007. Vangelder admitted having a few glasses, yet passed field sobriety tests. Vangelder then agreed to a preliminary alcohol screening Breathalyzer test which indicated that his blood alcohol content was 0.086 percent. He was then arrested and, at the station, produced another breathalyzer result of 0.08 percent blood alcohol content. Vangelder then submitted to a blood test which indicated that his blood alcohol content of 0.087 percent.

“I said I wanted to submit to a blood test,” Vangelder testified. “I didn’t think it was accurate. And the reason I say that is because I knew how much I had to drink.”

At trial, Vangelder called Dr. Hlastala to testify that breathalyzer results may produce blood alcohol content readings that can be above or below the suspect’s actual blood alcohol content.

“They are (inaccurate),” Dr. Hlastala testified before the judge. “And primarily because the basic assumption that all of the manufacturers have used is that the breath that [is] measured is directly related to water in the lungs, which is directly related to what’s in the blood. And in recent years, we’ve learned that, in fact, that’s not the case.”

The testimony was excluded and Vangelder was found guilty. An appellate court reversed the decision in 2011. San Diego City Attorney, Jan Goldsmith appealed the decision arguing that allowing such testimony would undermine Californi’s a per se law making it illegal to drive 0.08 percent blood alcohol content or higher.

“As noted earlier, we explained in Bransford, that the 1990 amendment of the per se offense was specifically designed to obviate the need for conversion of breath results into blood results — and it rendered irrelevant and inadmissible defense expert testimony regarding partition ratio variability among different individuals or at different times for the same individual,” Chief Justice Tani Gorre Cantil-Sakauye wrote for the court. “Whether or not that part of expired breath accurately reflects the alcohol that is present only in the alveolar region of the lungs, the statutorily proscribed amount of alcohol in expired breath corresponds to the statutorily proscribed amount of alcohol in blood, as established by the per se statute.”

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