The California Supreme Court has joined a handful of other courts in the country that have said Breathalyzer results mean different things for different people and ruled that suspected drunken drivers can attack the test results in court.
Defense attorneys lauded Thursday's unanimous ruling for deferring to science, which has shown for years that the test results are highly variable. Prosecutors, however, predicted the move will undermine California drunken driving cases.
At issue is how authorities use booze breath to determine how much alcohol is in the bloodstream.
When consumed, alcohol is absorbed in the blood and carried through the brain to the liver and heart before diffusing in the lungs, where it is exhaled in breath.
Authorities now use a nationally accepted scientific formula known as "Henry's law" to convert the amount of alcohol vapor in the lungs to a blood-alcohol level.
The scientific problem is that breath-to-blood ratios vary greatly throughout the population and fluctuate individually, influenced by such factors as body temperature, atmospheric pressure, medical conditions and the precision of the measuring device.