The California Supreme Court has joined with several other U.S. courts who say that Breathalyzer results mean different things for different people and will allow the test results to be attacked in court by persons suspected of driving under the influence.
The July 9 ruling was lauded by defense attorneys for deferring for science, which has shown for several years that test results can highly vary. But prosecutors argue that the move will undermine DUI cases in the state.
The center of the issue is how booze breath is used by authorities to determine the amount of alcohol in the blood stream.
Upon consumption, alcohol is absorbed into the bloodstream and carried through the brain to the liver and heart before diffusing in the lungs, where it is exhaled in breath.
A nationally accepted scientific formula called “Henry’s law” is currently used by authorities to convert the amount of alcohol vapor in the lungs to a blood-alcohol level.
However, the scientific issue with this method is that throughout the population, breath-to-blood ratios vary greatly and fluctuate individually, influence by factors such as body temperature, atmospheric pressure, medical conditions, and the precision of the measuring device.
Essentially what that means is that the same breath-test result for one person’s breath could mean intoxication, while for another person, it could simply mean one glass of wine with dinner.
The matter is complicated by California’s two distinct laws for DUI.
Under the first law, which has been on the books for decades, proof that a driver is intoxicated, such as slurred speech, bloodshot eyes, etc., is required. Jurors are informed that they can presume a person is drunk if blood tests reveal the blood-alcohol content to be at least 0.08 percent.
Under the second law, which the Legislature passed in 1981 and updated in 1989, a drunken driver is defined simply as a person whose blood-alcohol content is 0.08 percent, regardless of that person’s behavior. In 1994, the state’s Supreme Court extended that definition to include Breathalyzer results, which barred drivers charged with the second law from attacking the tests’ variability.
Since that time, the majority of DUI attorneys saw disputing Henry’s law as a dead end for challenging breath-test machines.
Person’s accused of DUI are typically charged by prosecutors with both versions of the law to increase the chance of conviction.
Similar rulings to the July 9 decision have been made in Arizona and Vermont.