[Blog editor;s note: Joshua Goldberg of Pittsburgh, PA writes into us to share information about Breath Alcohol Content machines.]
THE HISTORY OF BREATH TESTING: TWO ASSUMPTIONS AND A QUESTIONABLE SCIENTIFIC PEDIGREE. Part 1
Modern breath theory as proposed by prosecutor’s testing emanates from a 19th Century formula discovered by British physician and chemist William Henry. Referred to today by the term “partition ratio,” Henry’s formula (“Henry’s Law”) states: at a fixed temperature the solubility of a gas in a solvent is very nearly directly proportional to the partial pressure of the gas above the solution. Dominick A. Labianca, The Myth of Breath Test Accuracy: What the Studies Have Really Shown, DWI Journal, Vol. 5, No. 11. Nov. 1990 at 1.
Henry’s Law gone awry is modern breath testing. American scientists, law enforcement officers, and even government agencies pervert Henry’s formula by incorporating two basic assumptions into breath testing devices meant to standardize results for all test subjects: (1) the partition ratio for blood to breath alcohol is 2100:1; and (2) the constant temperature associated with the partition ratio is 34° C (an approximate “human body” temperature). While breath testing incorporates other assumptions, these two primary assumptions create an evidentiary landscape where the government cannot ascertain every defendant’s blood alcohol reading and transforms breath testing into a forensic discipline not “founded on a reliable scientific methodology.” cite
Assumption 1: Partition Ratio in Humans.
In 1984, the National Safety Council adopted a 2100:1 blood-breath partition ratio. It survives today. Id. at 2. The National Safety Council and the National Highway Traffic Safety Administration (NHTSA) utilize this “compromise number” to represent the mean or average population blood-breath partition ratio. Id. at 2; See also Kurt M. Dubowski, Absorption, Distribution, and Elimination of Alcohol: Highway Safety Aspects, 10 J. Stud. Alcohol Suppl. 101 (1985). When loaded into infrared spectrometry breath test devices, this basic mathematical assumption enables the devices to “automatically convert the results of a breath-alcohol analysis into a corresponding BAC.” Labianca, supra. at 2.
Partition ratios do not accurately apply equally to all humans. The government might argue that this ratio was selected to give defendants the benefit of the doubt (by underestimating defendant blood alcohol levels). See, Commonwealth v. Lane, 2008 Pa. Dist. & Cnty. Dec. LEXIS 287)(C.P. Chester County) (the breath test machine, as a result of its built-in scientific assumption, errs on the low side in a significant number of cases). Further, over the years, numerous studies opine that using a partition ratio of 2100:1 leads to the overestimation of blood alcohol concentration (BAC) for one in four to one in five test subjects. See generally, Labianca, supra. at 2-3, and Dubowski, supra. at 101-102.
How does a partition ration of 2100:1 overestimate blood alcohol results for a non-average defendant? Assume, hypothetically, a defendant’s unique partition ratio is 2300:1. The defendant blows into a breath testing device. The device then measures the alcohol contained in the defendant’s breath sample(s) through infrared technology. The breath testing device takes the infrared measurement, processes the data via a computer microprocessor, and (depending on the machine’s make and model) converts the breath alcohol concentration BrAC into a blood alcohol concentration (BAC). See, E. Martin Caravati and Katleen Anderson, Breath Alcohol Analyzer Mistakes Methanol Poisoning for Alcohol Intoxication, Toxiciology Case Report, Annals of Emergency Medicine, Vol. 55, No.2 (February 2010). During the computer’s conversion of the data from BrAC to BAC, it utilizes the 2100:1 partition ratio. The disparity between the 2100:1 ratio and the defendant’s unique 2300:1 partition ratio causes the breath testing device to miscalculate or overestimate the person’s blood alcohol content.
The adoption of the 2100:1 partition ratio makes modern day breath testing an unreliable “scientific methodology” without the “capacity to accurately analyze evidence and report findings” National Research Council. The use of the 2100:1 partition ratio means that the breath test device cannot accurately analyze every person’s blood alcohol level. Therefore, breath testing violates the National Research Council’s report first tenant.