The Top 20 Myths

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

Myth #6: Breath Test — Temperature Does Not Need To Be Measured

In all but a small number of jurisdictions, breath temperatures are not accounted for by the breath testing machines in use. Breath test devices are calibrated and checked with solutions heated to 34o C. If the defendant’s breath is higher than 34o C, the test reading will be falsely elevated.

As temperatures rise, the concentration of ethanol in the air phase increases and therefore the blood/air partition coefficient decreases. The average temperature coefficient of solubility for dilute solutions of ethanol in water and blood is 6.5% per 1o C for the temperature range of 20-40o C.
A.W. Jones., Effects of Temperature and Humidity of Inhaled Air on the Concentration of Ethanol in a Man’s Exhaled Breath, 63 Clinical Science 441, 441 (1982), citing, Kurt M. Dubowski, Breath-alcohol Simulators: Scientific Basis and Actual Performance, 3 Journal of Analytical Toxicology 177 (1979).


Defending against DUI / DWI

These results show clearly that mild hyperthermia in humans does . . . significantly distort the BrAC decay curve to an extent which would cause serious inaccuracy for prediction of BAC. The magnitude of this distorting effect of core temperature is too large (up to 23% with mild hyperthermia) to be ignored in breath-testing procedures. . . . Such error in the case of hyperthermia increases the likelihood of a suspect being unjustly convicted.
Glyn R. Fox & John S. Hayward, Effect of Hyperthermia on Breath Alcohol Analysis, 34 (4) Journal of Forensic Sciences 836, 839 (1989).

It is not only the defendant with a fever that is discriminated against.


Effective DUI / DWI Defense

Almost all (93%, 81%) of the collected breath samples acquired on the Alcotest 7110 MK IIIs had breath temperatures above 34o C. Our results show a breath temperature range of 32.4-36.2o C with a mean of 34.9o C. This is in agreement with the earlier work of Harger and Forney, Schoknecht and Stock who found mean breath temperatures of 35.1o C and 35o C, respectively.

Dale A. Carpenter & James M. Buttram, Breath Temperature: An Alabama Perspective, 9 IACT Newsletter 16, 16 (July, 1998). If Alabama defendants are indicative of defendants generally, then between 81 percent and 93 percent of breath tests nationwide are falsely elevated on the basis of temperature alone.


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Myth #7: Breath Test — Breathing pattern is not important

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