DUI Criminal Defense and The Blood-Breath Partition Ratio

Brian StrongBrian Strong, Criminal Defense Attorney in Arizona, DUI & Traffic Defense AttorneyLeave a Comment

DUI Breathalyzer TestArizona law states that “alcohol in the breath does not cause impairment; impairment results when alcohol enters the body, is absorbed into the bloodstream, and is transported to the central nervous system.” Guthrie v. Jones, 202 Ariz. 273, 274, 43 P.3d 601, 602 (App. 2002). None of my DUI clients struggle with this concept. Their struggle comes when instead of a blood test, a police officer has administered only a breath test. While breath tests are relatively cheap and much less invasive than an actual blood draw, breath testing suffers from several known flaws. One of the most contested issues in a DUI criminal defense are problems with the breath testing equipment involving the Blood-Breath Partition Ratio (the “Partition Ratio”).

In grade school, we learned that our blood is constantly being re-oxygenated as it passes through our lungs. When a person has alcohol in their blood stream, some of that alcohol escapes into the air sacks of our lungs. Hours after someone has stopped drinking, we can still smell alcohol on their breath because of this alcohol release coming from their lungs. The scientific question has always been: Is there a direct correlation between the amount of alcohol in a person’s blood and breath? This correlation has become known as the Partition Ratio.

In 1952, the National Safety Council’s Committee for Tests on Intoxication (now known as the Committee on Alcohol and Other Drugs) used rather primitive technology to proclaim that the “average” Partition Ratio was 2100 to 1. According to sixty year old science, 2100 milliliters of an average person’s breath sample would have the same amount of alcohol as 1 milliliter of that person’s blood. Common sense tells us that no one individual fits the mathematical “average.” And in spite of the National Safety Council’s disclaimers that individuals have unique and varied physiological components, the lawmakers of most states (including Arizona) wrote the 2100 to 1 Partition Ratio into the DUI statutes as if it were an incontrovertible scientific fact.

We have known for decades that Partition Ratios vary dramatically across the general population (anywhere from a low of 1600 to 1 to a high of 3200 to 1). Not only are we different, but one person’s Partition Ratio can fluctuate significantly over time. A Partition Ratio ten minutes after drinking will change dramatically just thirty minutes later. Because any breath test taken within two hours after driving is admissible in a DUI trial, this scientific fact is especially troubling.

Studies have also shown that just a few degree changes in breath temperature can significantly alter an individual’s Partition Ratio. As a result, if you have a low-grade fever, your breath test gets skewed. Who in Arizona has not been dehydrated at one time or another? Yet, even mild dehydration can significantly alter a person’s Partition Ratio because there is less liquid in the blood stream.

DUI Defense attorneys constantly seek to have our clients treated as individuals in the judicial process. Lawmakers and prosecutors are just as active in treating us as if we have all been forged from the exact same cookie-cutter mold. In August of 2013, the Arizona Supreme Court decided that both general and individual Partition Ratio evidence would be admissible to show the lack of impairment in certain DUI offenses. In State v. Cooperman, 232 Ariz. 347, 306 P.3d 4 (2013), the State argued that the 2100 to 1 Partition Ratio created a legal presumption that the defense can never attack. The Supreme Court rejected this argument by noting that in criminal cases, our state constitution demands that all presumptions are subject to being rebutted with the appropriate evidence. 232 Ariz. at 351, 306 P.3d at 8. Although not applicable to all DUI offenses, Cooperman has been instrumental in bringing more individualized justice to the Arizona DUI courts.

For a scholarly review of the science behind the Partition Ratio, see: Hlastala, Physiological Errors Associated With Alcohol Breath Testing; www.mphlastala.com/Champion.pdf

If you or a loved is ever arrested for DUI Alcohol, please give our experienced DUI Criminal Defense attorneys a call at 480-833-2341.

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Attorney Profile: Brian D. Strong, Arizona DUI Attorney

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