In People v. Vangelder, --- Cal.Rptr.3d ----, 2011 WL 2583854 (Cal.App. 4 Dist.) the appellate court found in error the trial court's ruling disallowing any expert testimony from defendant that would have presented a physiologist's scientific criticisms of the reliability of the data produced by breath test machines, which are based on the assumption that such devices only measure alveolar (deep lung breath) air.
Defendant's offer of proof from his expert would have provided testimony that this assumption is not always justified, and that a series of physiological factors (e.g., individual breathing patterns, body temperature, blood hematocrit, and breath temperature) 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.
As the appeals court recognized, "[i]t must be emphasized that defendant is not arguing that the EC/IR breath test device was malfunctioning, out of order, or incorrectly operated, but instead, he challenges the validity of its design, operation, and sampling method."
Due to the excellent summarization of Dr. Hlastala's testimony, and the scientific basis for it, DAD recommends that the reader review the entire opinion for its value to the profession.
The appellate court explained why the expert testimony was admissible as follows:
"Although breath test results are admissible if a reliable foundation for them is laid, we think that such competent evidence of their potential inaccuracy, because of physical variabilities leading to poor data in sampling, should have been allowed to be considered, as going to the weight to be accorded the testing results. (See 90 A.L.R.4th 155, § 2, p. 164.) In light of the authorities described above, we conclude that the trial court was mistaken in stating that this expert testimony was completely irrelevant as an attempt to rebut the breath test result, for either the per se or generic DUI counts. Under section 23610, subdivision (c), this expert provided enough of a foundation to explain why he believes that the breath test samples were not representative, based upon the problems in obtaining the samples that were inherent within the identified variables of an individual's physiology. The expert was proposing that even a correctly operating breath test device would take in samples that were essentially inaccurate and nonrepresentative of breath-alcohol content, which was ultimately to be converted into a blood-alcohol reading through the use of the partition ratio. He did not have to indicate which way the potential inaccuracy would point, as a foundational matter, in order to cast doubt on this part of the testing method. Even a small error could possibly turn a marginally legal reading into an illegal reading. (See 90 A.L.R.4th 155, § 2, p. 161.)"Concluding that the exclusion was error, the court stated:
"When the court excluded this expert evidence, the error was not harmless because it was “reasonably probable that a result more favorable to [defendant] would have been reached” had such evidence been admitted. ( Watson, supra, 46 Cal.2d 818, 836.) First, defendant performed well on the physical field sobriety tests. He was driving skillfully and pulled over as soon as the red lights went on. There were identifiable problems with the other two chemical tests given, the PAS test and the blood test, with reference to the timing of administration and the time of driving. Defendant gave a revised drinking history. The jury questioned whether it could convict on a per se count but not a generic count, showing they had some confusion. All of those factors point to probable prejudice in the exclusion of this expert testimony, since it could have shed light upon the accuracy of the EC/IR breath test results or the PAS tests, as they affected the proof of each DUI count charged."
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