San Diego DUI Breath Test Defense Lawyer

Errors in Breath Tests That Can Cause You to be Charged With DUI

There are many possible sources of error in a breath test. The developers of breath testing for alcohol made universal assumptions about the people being tested, which are not, in fact, universally true. This can cause a breath test result to indicate that a given person's blood alcohol content was .08 or more when the true blood-alcohol content was below .08.

Partition Ratio

One of a number of assumptions made by breath testing devices in California concerns what is known as the breath-to-blood ratio, or partition ratio. The partition ratio is the ratio between alcohol dissolved in the blood and alcohol exhaled in the breath. In California, breath testing is based on an assumption that every subject tested has a partition ratio of 2100 to 1. Believe it or not, this scientific convention was arrived at in 1953, the early days of black and white TV, and the movie Invaders from Mars.

However, individual partition ratios range greatly, from 1200 to 1 to 4100 to 1. The "average" partition ratio is about 2,280 to 1. Thus, while the assumed partition ratio of 2100 to 1 gives some people tested a slight break, its use causes other people to end up with an inflated blood alcohol result. For this reason, a number of countries have abandoned use of the 2100 to 1 ratio as a standard. A safer ratio would be 1500 to 1. For approximately 97% of the population, this would not result in an inflated BAC.

Another complicating factor is that a person's partition ratio is not static, but changes throughout the day. Studies by Dr. A.W. Jones indicate that an individual's partition ratio is a moving target. This was recognized by the California Supreme Court in the recent People vs. Mc Neal case. In fact, one's partition ratio can even vary over the course of a breath of air, with the partition ratio dropping at the end of an exhale.

There is a great deal more to breath testing problems in the partition ratio area. Results may be temperature dependent. There can be variations with the type of blood measured. There may be changes over time. Gender can have an impact.

It is possible for an accused person in a DUI case to undertake his or her own partition ratio study at a forensic toxicology laboratory. Such a study could be extremely useful in the defense of a DUI charge.

If you've been charged with drinking and driving in the San Diego area, you need a strong defense from an attorney who understands how testing errors and medical conditions can cause false readings. With 25 years of DUI defense experience, you will find the aggressive legal advocate you need at The Law Office of Mark R. De Yoe.

DUI defense attorney Mark R. De Yoe will do a thorough review of your case, looking at every possible area of defense. He has handled thousands of DUI cases in his decades of legal work in San Diego courts, including downtown San Diego, Chula Vista, El Cajon and Vista. He is not only well versed in defense strategy; he also knows the local courts and judges.

You May Have Grounds for Dismissal

Don't assume the breathalyzer test is always right. If the person who administered your test did not follow exact procedures, this may be grounds for dismissal. You may have more defense options than you know. Call San Diego DUI attorney Mark R. De Yoe at (619) 894-8295 to schedule a consultation email him.