Breath testing, as currently used, is a very inaccurate method for measuring BAC, Even if the breath testing instrument is working perfectly, physiological variables prevent early reasonable accuracy….Breath testing for alcohol using a single test method, should not be used for scientific, medical or legal purposes where accuracy is important. (Hlastula, Physiological Errors, Associated with Alcohol Breath Testing, 9(6) The Champion 19 (1985).)
A number of scientists who have conducted studies of breath-alcohol analysis have concurred with Dr. Hlastala in concluding that the method is inherently unreliable. Thus, for example, a recent study determined that breath readings vary at least 15 per-cent from actual blood-alcohol concentrations. Simpson, Accuracy and Precision of Breath-Alcohol Measurements for a Random Subject in the Postabsorptive State, 33(2) Clinical Chemistry 261 (1987). Furthermore, at least 23 percent of all individuals tested will have breath results in excess of true blood-alcohol levels. The author concluded that, “[g)iven the choice, it would seem that if a conclusion is to be made about the BAC of a random subject, especially when the conclusion can have serious consequences, it would be far preferable to make it on the basis of a direct [blood) measurement. . . ."
In another study, conducted by members of the toxicology section of the Wisconsin State Laboratory of Hygiene, only 33 percent of the breath test results correlated with corresponding blood tests. Reported in 32(4) journal of Forensic Sciences 1235 (1987), the study involved a survey of 404 actual cases in Wisconsin in which defendants had been tested on a Breathalyzer (either the Model 900 or 900A) as well as by blood analysis. The two tests were considered to correlate when there was a difference of .01, percent or less.
One interesting aspect of the study was that in 11 of the cases, the defendant was shown to be intoxicated using one of the tests but not intoxicated when using the other.
At least one court has even reversed DUI convictions on the grounds that breath tests are inherently unreliable. In State v. McGinley, 550 A.2d 1305 (N.J. Super. 1988), the New Jersey Superior court, Law Division, considered the consolidated appeals of four defendants whose convictions involved Breathalyzer tests. Although noting that the New Jersey Superior Court had essentially taken judicial notice that the Breathalyzer models "900 and 900A are scientifically reliable," the court nevertheless felt free to consider new scientific evidence not previously available — evidence based in large part on the work of Dr. Kurt Dubowski:
The scientific evidence upon which the defendants rely shows the following:
- The breathalyzer is designed to test persons having a 2100/1 blood-breath ratio. Such ratios in fact vary from 1100/1 to 3200/1 and the variance can produce erroneous test results. High readings are produced in 14% of the population.
- The temperature of the machine itself varies, affecting test results.
- Body temperatures vary, affecting test results.
- Hematocrit (the solid particles in whole blood) levels vary, particularly between males and females, affecting test results. These sources of error make breathalyzer test results suspect and, to insure reliability, require the substantial reduction of blood-alcohol percentages based on a translation of those results. The leading expert in the field, recognized as such by both State and defense, is of the opinion that the reduction should be .055. [1350 A.2d at 1306.]
Dr. Dubowski has long advocated strict procedures for minimizing the many sources of error in breath testing. In a recent article entitled Quality Assurance in Breath-Alcohol Analysis, 18 Journals of Analytical Toxicology 306 (October 1994), he identified four “necessary safeguards” for breath testing:
- A pre-test deprivation-observation period of’ at least 15 minutes (set the discussion of mouth alcohol in 8.1.4);
- Blank tests immediately preceding each breath specimen collection step;
- Analysis of at least two separate consecutive breath specimens, taken two to ten minutes apart (different results from duplicate analysis may indicate such problems as ratio frequency interference; see 8.1.9);
- An appropriate control test accompanying every subject test (see 8.1.9 for a discussion of calibration using a simulator).
Due largely to the inherent unreliability of breath analysis, the National Safety Council Committee on Alcohol and Other Drugs has recommended that at least two separate breath samples be collected and analyzed individually. As reported in a letter from Dr. Dubowski published in 9 American Journal of Forensic Medical Pathology 272 (1988), the Committee further recommended that the breath samples be collected at intervals of at least two and not more than ten minutes. This process of duplicate analysis has been widely advocated by experts in the past, most notably (and vociferously) by Dr. Richard Jensen.
Whether acceptably accurate or not, breath analysis is the most convenient and economical method for the police, and the most convenient and least embarrassing or painful for the arrestee. As a result, counsel will probably encounter some sort of breath analyzing instrument in 70 to 80 percent of his drunk driving cases. There are a number of different breath analyzing machines in use today. The most commonly encountered of these is the Intoxilyzer Model 5000, of which there are now a number of different versions (see 8.2.1), The second most popular of the machines is the Intoximeter 3000 (see 8.2.2), followed by the older version of the 5000, the Intoxilyzer 4011 (and its various permutations), The BAC Datamaster/Verifier (see 8.2.3) is now universally used in Washington, South Carolina, and Vermont, and is found sporadically in other states as well. Finally, the old 900/ 900A series of Breathalyzers are still found in a few jurisdictions. Each of these machines utilizes its own mechanism for analyzing the alcoholic content of exhaled vapor. With the exception of the Breathalyzer, however, all use a common method: infrared spectroscopic analysis (the Breathalyer employs the “wet chemical” technique). These machines operate on the principal that alcohol vapor captured in a chamber will absorb light waves of a certain frequency when beamed through it. The more alcohol present in the chamber (i.e,, the higher the percentage of alcohol in the breath sample), the more light is absorbed. In theory, then, determining the alcohol concentration of the sample is simply a matter of measuring the amount of light that reaches a receptor at the other end of the chamber; the more light, the lower the alcohol content in the breath. A computer then translates the figure into blood-alcohol concentration, using the blood-breath partition ratio (see 8.1.1).
In approaching a case involving a breath analysis, counsel should be aware that there are a large number of potential problems, both theoretical and operational. As has already been seen in 8.0 et seq., there exists a broad range of factors that can render any result of blood-alcohol analysis – breath, blood, or urine – unreliable. As seen in the following subsections, additional problems unique to breath analysis add to this unreliability,
Thank you to Lawrence Taylor for providing the above information. For more information on DUI Defense, please see Lawrence Taylor’s Los Angeles DUI Law website.
This is an excerpt from Drunk Driving Defense, 5th edition by Lawrence Taylor (New York: Aspen Law and Business, 800-638-8437)