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Breathalyzer tests can be challenged, Calif. Supreme Court rules

July 9, 2009 | 11:24 am

The California Supreme Court made it easier today for persons accused of drunk driving to challenge the results of breathalyzers.

The state high court ruled unanimously that defendants can present evidence to show that the breathalyzer results failed to accurately reflect the amount of alcohol in the driver's blood.

A suspected drunk driver can choose either to submit to a blood test, which measures the amount of alcohol in the blood, or a breath test. A breath sample must be converted mathematically to derive a blood-alcohol percentage.

The conversion factors can vary widely, "both in the general population and within an individual," the court said.

A driver's ratio of breath-alcohol to blood-alcohol concentration can be influenced by body temperature, medical conditions, sex and the precision of the measuring device.

Whereas experts say the standard ratio used to derive a blood-alcohol concentration from breath approximates or even underestimates the amount of alcohol the driver consumed, they also agree that breathalyzer results may not always accurately show an individual's intoxication.

"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, Justice Carol A. Corrigan wrote for the court.

-- Maura Dolan