San Francisco DUI Lawyer Files: Expert Testimony Concerning Physiological Variability Affecting Breath Testing Improperly Excluded

 Posted on May 01, 2012 in DUI

San Francisco DUI Lawyer Paul Burglin offers this case example:
Expert Testimony Concerning Physiological Variability Affecting Breath Testing Improperly Excluded
People v. Vangelder (2011) ___Cal.App.4 ^th ___ (Fourth Dist. COA – Docket No. D059012 (Note: Petition For Review has been filed and the decision is not yet final)

Defendant appealed the trial court's exclusion of physiologist Michael Hlastala's scientific criticisms concerning the reliability of the data produced by breath test machines which assume the breath samples measure only alveolar (deep lung breath) air. Defendant's offer of proof was that the assumption is not always valid due to a series of physiological factors (e.g., individual breathing patterns, body temperature, blood hematocrit, and breath temperature) that may affect the transmission of alcohol in gas form, from the bloodstream to the lower and upper portions of the lungs, to the trachea and mouth and back again, thereby making such breath measurements unreliable, and undermining, in turn, the application of the standardized partition ratio calculation for converting breath levels to blood-alcohol levels.

Held : The trial court prejudicially erred in refusing to allow scientific testimony to be presented that would have raised doubts about the reliability of the EC/IR and PAS breath testing devices, with respect to the physiological variables that can affect the sample of breath or air taken.

Distinguishing the California Supreme’s Court’s prior decision in People v. Bransford (holding that evidence of partition ratio variability is irrelevant and inadmissible on the per se charge (i.e., driving with a.08 percent or higher alcohol content), the Court noted that this was not an attack on the partition ratio employed, but rather a critique on the assumed nature and quality of the breath samples.