High Court Limits Testimony About Breath Tests In California

In this case the accused was arrested and charged with DUI and driving with a .08 or more.  At trial he hired one of the top breath testing experts in the country to testify about the unreliability of breath tests, the Judge would not allow it.  He was convicted and appealed.  The Supreme Court found no error with the trial court ruling as to the exclusion of testimony. Section 23152, subdivision (b) prohibits driving with either the specified blood-alcohol level or the specified breath-alcohol level. The statute defines the .08 percent breath-alcohol offense in light of the standard partition ratio, which the Legislature adopted based on studies correlating breath samples to the concentration of alcohol in the blood. The expert's testimony challenging the reliability of breath-testing machines generally because they fail to measure the alcohol content of the air from the alveolar region of the lungs was fundamentally at odds with the statutory per se offense. The statute and California Code of Regulations, title 17, section 1219.3 simply require a breath specimen consisting of the last portion of expired breath that is captured by an approved breath-testing machine that is properly calibrated and employed. A defense expert may not invite a jury to nullify the Legislature's determination about the fundamental reliability of approved breath-testing models. Other proposed defense expert testimony about physiological factors that may affect the results of breath-testing machines generally essentially constituted partition ratio variability evidence, which is barred in per se DUI prosecution