California Supreme Court bars expert testimony on the scientific unreliability of breathalyzer tests

A California trial judge presiding over the OUI trial of People v. Vangelder was recently affirmed by the California Supreme Court when he prevented a jury from listening to expert testimony on the general unreliability of scientific techniques underlying breathalyzer tests. If appealed to the U.S. Supreme Court, this decision could limit or exclude expert testimony on the scientific unreliability and inaccuracy of breathalyzer tests across all jurisdictions, abolishing what can be a strong defense against an OUI charge.

In the matter of People v. Vangelder, a state officer clocked Vangelder driving late into the night on a speeding on a state highway. After following Vangelder for a few miles without observing any signs of intoxication, the officer pulled Vangelder over to the shoulder of the road. Vangelder was fully compliant with all of the officer’s instructions. After being questioned, Vangelder told the officer that he had three glasses of wine at dinner, and that he was just goofing around on the road.

Vangelder passed all field sobriety tests, and then submitted to preliminary breathalyzer tests. The results came in at 0.095 and 0.086. After Vangelder was arrested (the state limit is 0.08) and transported to the station, he submitted to two more breathalyzer exams which returned a reading of 0.08. Vangelder was charged with two misdemeanors – a generic OUI offense, and the more specific offense of driving with a BAC reading above 0.08 percent – despite the inconsistencies in the BAC readings.

During his trial, Vangelder introduced a prominent expert in the field of human physiology and alcohol consumption. This expert witness testified that breathalyzer tests are generally scientifically unreliable measures of blood alcohol content because they do not measure the alcohol directly. Instead, according to the expert, breathalyzer tests rely on an individual’s breath at the time of the test, and since a breath may contain several traces of alcohol from sources other than the driver’s blood, the test is inaccurate.

The trial judge instructed the jury to disregard the expert’s testimony regarding the scientific accuracy and reliability of breathalyzer tests. The jury returned a guilty verdict with regard to the specific offense, but were unable to reach a verdict with regard to the generic charge of driving under the influence.

While the trial was conducted, the California Supreme Court decided on the case of People v. McNeal, where it held that expert testimony on the scientific technique underlying breathalyzer tests is is inadmissible with respect to the more specific offense of driving with a BAC over 0.08 percent, but is only admissible with regard to the generic offense to rebut the presumption that the driver’s BAC level was over 0.08 percent while driving. When Vangelder’s appeal was raised before the California Supreme Court, the Court elaborated on its earlier decisions and affirmed the exclusion of the expert testimony.

The California Supreme Court explained that the issue of whether the science underlying breathalyzer tests was reliable had already been addressed by the State legislature when it enacted the statutory offenses. Because the legislature was aware of possible conflicts in the underlying science, but still decided to use breathalzyer tests as a measure of a driver’s intoxication for the purpose of these offenses, any expert testimony on the reliability of breathalyzer test readings as accurate measures of blood alcohol content is irrelevant.

Under these decisions, if Vangelder wanted to effectively challenge the breathalyzer test, his expert should have testified as to the inaccuracies of the particular breathalyzer device used to test Vangelder’s breath. The court’s decision only allows the expert to testify that the particular device used on Vangelder was not calibrated, malfunctioned, or improperly used by the testing officer. But since Vangelder’s expert stated that he was unable to determine whether the machine was accurately reading Vangelder’s breath, his testimony could not defeat the breathalyzer test results.

If this California decision is upheld by the U.S. Supreme Court, Massachusetts OUI defense attorneys may face similar exclusions to expert testimony, which will undercut a major defense. The outcome will depend on how Massachusetts courts interpret the statutory language of OUI offenses, and the intent of the state legislature to incorporate breathalyzer test results as accurate measures for the purposes of the offense. As a general rule of thumb, however an OUI Lawyer should use expert testimony to question the reliability of the actual device used by officers to read a defendant’s breath, rather than simply to raise a whole-sale issue of the scientific reliability of breathalyzers to accurately measure BAC. Even if the defense attack is on the general unreliability of breath test evidence, the right of cross examination and the right to a fair trial should make such testimony admissible at trial with the jury to access the weight to be given to the testimony.

Contact Information