Another Court Challenges Breath Tests

The California Supreme Court has become the latest appeal court to rule that breath testing machines can produce different results for different people and can be attacked in court by suspected drunken drivers. Courts in Arizona and Vermont have made similar rulings.
At question is the way the breathalyzer machines convert the amount of alcohol vapor in the lungs to an estimate of the level of alcohol in the blood.

The breath-test machines use a scientific formula known as "Henry's Law" to estimate blood alcohol content by the amount of alcohol in the lungs. But scientists say breath-to-blood ratios vary greatly from person to person and can fluctuate due to many factors include body temperature, atmospheric pressure and even some medical conditions.

Attacking Henry's Law

Many states have passed "per se" laws that state that anyone who records a blood-alcohol level of .08 is guilty of driving under the influence regardless of any other behavior or appearance. In other words, someone who displays no visible signs of intoxication can be charged and convicted for DUI based solely on their breath-test results.

In California specifically, the state Supreme Court ruled in 1994 that drivers could not challenge the variability of the breath tests in court. Therefore, most defense attorneys have dropped the practice of attacking Henry's Law.

This latest ruling opens the door again for those challenges and was a welcomed ruling by attorneys who specialize in drunk driving cases.

But law enforcement officials and prosecutors said the ruling will make it much more difficult to gain convictions in cases involving driving under the influence.

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