The Top 20 Myths

of Breath, Blood and Urine Tests You need to know to defend when DUI/DWI convicted

Myth #5: Breath Test — Reporting BAC As BrAC Cures Blood: Breath Ratio Problems

Again, Dr. Simpson needs no interpretation.

The enactment of direct breath-alcohol statutes, however, has not eliminated the need to correct for the experimental error stemming from the conversion of breath- into blood-alcohol concentration via multiplication of the former by a constant blood/breath ratio. In fact the enactment of such statutes has ... resulted in the legislation of incorrect science.
Dominick A. Labianca & G. Simpson, Medicolegal Alcohol Determination: Variability of the Blood- to Breath-Alcohol Ratio and Its Effect on Reported Breath Alcohol Concentrations, 33 Eur. J. Clin. Chem. Clin. Biochem. 919, 919 (1995).



Defending against DUI / DWI

A statute that establishes a specific breath-alcohol concentration limit in this way does not solve the problem of blood/breath ratio variability that Dubowski and Jones sought to eliminate. It simply ignores that variability, which is the essence of its scientific flaw.
Id. at 919-20.

Moreover, since the statute operates under the assumption that any driving-while-intoxicated suspect who undergoes a breath test is characterized by a 2100:1 blood/breath ratio, it is also legally flawed; if the statute does ‘greatly enhance the investigation and disposition of [driving while intoxicated] charges’; as claimed by Dubowski, it does so by inappropriately relieving the prosecution of its burden to establish that the defendant has a blood/breath ratio of 2100:1 at the time of the breath test.
Id. at 920- 921.


Effective DUI / DWI Defense

The only approach at present is to use population data for blood/breath ratios corresponding to appropriate confidence limits. As recently stated by Rainey . . . mean ± 2.58 SD (99% confidence limits) is the appropriate confidence interval for conversions of body-fluid alcohol concentrations when a standard of ‘beyond a reasonable doubt’ is required.
Id. at 921.

Applying the 2.58 standard deviation concept for 99 percent reliability, using Dr. Dubowski’s figures, a reported BrAC (breath alcohol concentration) of .10 would instead be reported as .0789.3


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Myth #6: Breath Test — Temperature does not need to be measured

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