Metropolitan News-Enterprise


Friday, July 10, 2009


Page 3


S.C.: Suspected Drunk Drivers Can Challenge Breathalyzer Tests


From Staff and Wire Service Reports


The California Supreme Court yesterday ruled that a man convicted of driving under the influence of alcohol should have been allowed to present evidence of how the ratio used to derive a blood-alcohol percentage from a breath sample may have yielded an inaccurate representation of his blood-alcohol level in order to rebut the presumption that his blood-alcohol concentration affected his ability to drive safely.

But, in a unanimous decision affirming the Fourth District Court of Appeal, the high court upheld Timmie McNeal’s conviction, ruling that the exclusion of the proffered evidence challenging the breathalyzer results was harmless.

California breath testing machines use a nationally accepted scientific formula known as “Henry’s law” to convert the amount of alcohol vapor expelled from a suspected drunk driver’s lungs into a blood-alcohol level.

It is based on a mathematical constant—known as a partition ratio—of 2,100-to-1, meaning the amount of alcohol in 2,100 milliliters of breath is presumably equivalent to the amount of alcohol in one milliliter of blood.

However, breath-to-blood ratios vary greatly throughout the population and fluctuate individually, and can be influenced by such factors as body temperature, atmospheric pressure, medical conditions and the precision of the measuring device.

McNeal’s breath sample indicated a blood-alcohol concentration of 0.10 percent, and he was charged with a “generic DUI” for driving while impaired by alcohol, and a “per se DUI” for driving with a blood-alcohol level of 0.08 percent or more.

Motion to Reopen

At trial before San Bernardino Superior Court Judge Michael A. Smith, after both sides had rested but before closing arguments, McNeal moved to reopen in order to present expert testimony about partition ratio variability in connection with the generic DUI charge.

Smith denied the motion and instructed the jury regarding the statutory presumption of intoxication, which provides that a driver is presumed to have been driving while impaired by alcohol if a chemical test measures the driver’s blood alcohol at 0.08 percent or more.

The jury convicted McNeal on the generic DUI charge but hung on the per se count.

McNeal moved for a new trial, arguing that he should have been permitted to introduce expert witness testimony  that 30 percent of the population has a partition ratio other than 2,100-to-1 in order to rebut the presumption he had been intoxicated.

After Smith denied the motion, McNeal appealed to the Superior Court Appellate Division. The appellate division ruled the partition ratio evidence was relevant and admissible, but found the error in excluding it harmless in light of the evidence supporting the jury’s verdict.

The Fourth District Court of Appeal then transferred the case to itself on its own motion. Div. Two differentiated evidence about the variability of partition ratios in the general population from evidence showing that an individual defendant had a nonstandard ratio and concluded only the latter was admissible.

The court reasoned that if the defendant’s own ratio differed significantly from the standard ratio, this fact could support an inference that the defendant was not actually impaired at the time of the offense.  The court therefore held such personal partition ratio evidence is relevant and admissible in generic DUI cases. 

Offer of Proof

Although it found that McNeal’s offer of proof was insufficient to determine the precise nature of the partition ratio evidence he sought to introduce, the Court of Appeal assumed that he had intended to present evidence about his own ratio and ruled, assuming he had preserved the issue for review, that any error in excluding such evidence was harmless.

Writing for the California Supreme Court, Justice Carol A. Corrigan said that this distinction was unnecessary as both types of evidence challenge the accuracy of a defendant’s reported blood-alcohol level and both could be used to support an inference that, despite a high breath test result, the defendant was not under the influence.

She noted that People v. Bransford (1994) 8 Cal.4th 885 held that evidence about partition ratio variability was irrelevant in per se DUI cases because the Legislature incorporated a 2,100-to-1 partition ratio within its definition of the offense, but reasoned Bransford would not bar such evidence in generic DUI cases as the ratio is not part of the definition of that offense, but is part of a rebuttable presumption.

Thus the ratio, like the rest of the presumption, is rebuttable, she said.

‘Competent Evidence’

As the crime of a generic DUI requires evidence that a driver was in fact impaired by his consumption of alcohol and he is entitled to offer “competent evidence” showing he was not under the influence of alcohol, Corrigan explained that a driver could do so by raising a reasonable doubt as to whether the test result was an accurate measure of his blood-alcohol level.

“Evidence casting doubt on the accuracy of the breath-to-blood conversion ratio is just as relevant as other evidence rebutting the presumption of intoxication from a breath test result, such as evidence that the defendant had a high tolerance for alcohol or performed well in field sobriety testing,” she wrote, adding that courts in Arizona and Vermont have made similar rulings.

But in McNeal’s case, Corrigan concluded that the exclusion of his proffered partition ratio evidence, though erroneous, was harmless in light of the “significant evidence” of his intoxication.

Corrigan also cautioned that partition ratio evidence may not be used to negate the basic fact triggering the presumption. Because the generic DUI offense incorporates the 2,100-to-1 partition ratio, a driver may not argue the presumption does not apply because a different ratio should have been used, she said.

The court declined to reach the issue of whether a contrary interpretation of the generic DUI offense would raise constitutional concerns or whether evidence of an individual’s personal partition ratio has gained sufficient acceptance in the scientific community to be admissible.

Santa Barbara Deputy District Attorney Margaret O’Malley, who represented the California District Attorneys Association before the high court, criticized yesterday’s ruling. “It will confuse jurors,” she said. 

But Steven Oberman, a Tennessee lawyer and founder of the National College for DUI Defense, indicated that the ruling simply confirms what scientists already knew: one-size-fits-all breath tests don’t necessarily reflect reality for all suspects.

“I’ve had clients with one lung,” he said, explaining such people will naturally have more alcohol vapors in their breath than someone with two lungs.

The case is People v. McNeal, 09 S.O.S. 4197.


Copyright 2009, Metropolitan News Company