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Why Do Lawyers Tell People to Refuse Breath Tests?

Many people are uncertain why lawyers advise clients to refuse a breath test.  Most lawyers who are familiar with the studies conducted on breath testing machines know that these machines are not infallible.  In fact, many scientific studies demonstrate an alarming false positive rate and other significant concerns. 

These studies indicate that there are significant error factors in a breath test.

One large study called the “Harger Study” found that less than 50% of breath tests are within 10% of the actual blood alcohol level.  These studies were done with breath test machines and corresponding blood tests and in a  controlled setting.   It is fair to say that it is impossible to get perfectly accurate and reliable BAC tests based upon breath analysis. 

Moreoever, there are a host of known sources of error.  Here is a classic list many lawyers like to cite which is found in Defending Drinking Drivers (Vol. 1, Section 223.8, 2007), Patrick Barone and John A. Tarantino:

Sources of Error in Breath Testing

There are many factors that can affect the validity of breath analysis. Some of the problems that can arise during a breath test are:

(1) operator error (which can include the failure to observe the subject for the required period of time before administering the test or the failure to follow the administrative rules and regulations concerning the administration of a breath test).

(2) deviations from normal body temperature. See LaBianca, “The Myth of Breath Test Accuracy What the Studies Have Really Shown,” 5 DWI Journal: Law & Science 11 (November 1990) (for every one degree centigrade change in alveolar air temperature, the conversion ratio, and the percent blood alcohol content changes by 6.5%); see also Jones, “How Breathing Technique Can Influence the Results of Breath Alcohol Analysis,” 22 Med. Sci. Law 275-280 (1982),

(3) abnormal hematocrit. See generally E. Fitzgerald & D. Hume, Intoxication Test Evidence: Civil and Criminal (1987 & 1990 Supp.);

(4) disease. See Cohen, “Calculation of Blood Alcohol Concentration: Uses and Limitations,” 1 DWI Journal: Law & Science 5 (1986);

(5) changes in barometric pressure. See Leonelli, et al, “Altitude Effect on Alveolar Ethanol Analysis,” 40 Aeros. Med. 1388 (1969);

(6) hyperventilation. See Schmutte, “Comparative Study of Breath and Blood Alcohol Concentration After Physical Exercise and Special Breath Techniques (Hyperventilation),” 10 Blutalkohol 34 (1973); Jones, “How Breathing Technique Can Influence the Results of Breath-Alcohol Analysis,” 22 Med. Sci. Law 275-280 (1982);

(7) improper machine maintenance. See Cowan, Hayne & Fox, “Attacking the Reliability of Breath Alcohol Testing Devices: A Case Study of the BAC Datamaster II,” DWI Journal: Law & Science 9 (September 1987);

(8) problems with simulators. See Dubowski, “Breath Alcohol Simulators: Scientific Basis and Actual Performance,” 3 J. Anal. Tox. 177 (1979); Ramsell, “Impeaching 10,000 Breath Alcohol Tests: The Solution is the Solution,” 4 DWI Journal: Law & Science 2 (February 1989); and

(9) radio-frequency interference.

Accordingly, before a judge or jury decides how much weight to afford a motorist’s breath sample, it is crucial that these issues be explored and explained.  Unless you are in Ohio where a 1984 Ohio Supreme Court prevents an accused from challenging the reliability of breath test machines on issues like these.  (State v. Vega, 12 Ohio St.3d 185, 1984)

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