Breath Testing

After a driver is arrested for an alcohol related DUI he or she will undoubtedly be requested to submit to an evidential breath test at the police station or other location.

The admissibility of an evidential breath test is governed by RCW 46.61.506. The prosecution must satisfy eight foundational requirements. In general those requirements are:

  1. The officer must be authorized by the state toxicologist to perform the breath test;

  2. The driver must not have anything to eat, smoke, or drink, or must have not vomited within fifteen minutes of taking the test;

  3. No foreign substances can be in the person’s mouth at the start of the fifteen minute observation period;

  4. The liquid simulator solution must have a temperature within .3 degrees centigrade of thirty-four degrees;

  5. The message “verified” must be shown with respect to the internal standard test;

  6. The two breath samples must be within plus or minus ten percent of their mean;

  7. The liquid simulator solution result must be between .072 and .088;

  8. Four blank test results of .000 must result (before testing, between the two breaths, and after the last breath sample). RCW 46.61.506(4)(a).

Unfortunately, the court must assume the state’s foundational facts are true and must view such facts in a light favorable to the prosecution. RCW 46.61.506(4)(b). This makes suppressing a breath test a difficult task. But bad breath tests can and will happen. Operator error, equipment malfunction, and numerous other issues may negate the above foundational requirements and support a motion to suppress. For example, even one minute less than the required 15 minute observation period will require a breath test to be suppressed. See, e.g., State v. Baker, 56 Wash.2d 846 (1960). Breath tests may be suppressed for other reasons beyond the state’s failure to lay an adequate foundation concerning the statutory elements discussed above. For example, a person arrested for DUI has a statutory right to refuse breath tests. RCW 46.20.308(2); State v. Bostrom, 127 Wash.2d 580, 590 (1995). The decision whether to refuse or submit to the breath test must be knowing and intelligent. State v. Whitman County Dist. Ct., 105 Wash.2d 278, 282 (1986). Therefore, an officer’s failure to properly advise a driver of implied consent warnings necessary to enable one to make a knowing and intelligent decision may support a motion to suppress. Also, even if the state satisfies the statutory foundational elements discussed above, a trial court may still exclude breath test results under the rules of evidence if there is a precise problem identified by the defense that would render the test unreliable. See City of Fircrest v. Jensen, 158 Wash.2d 384 (2006).

Regardless of admissibility, the accuracy and reliability of breath tests may be attacked at trial. The BAC Datamaster uses infrared spectroscopy to measure a person’s breath alcohol concentration. Basically, the BAC Datamaster is designed to measure deep lung air or “alveolar air.” The person giving a breath sample must breathe deep lung air which travels into the sample chamber of the BAC Datamaster. Then a narrow infrared light is shined through the sample chamber and the breath sample contained therein. The deep lung air (particularly ethanol therein) absorbs the infrared light. Breath alcohol concentration is calculated based on the difference between the amount of infrared light absorbed with the deep lung air in the sample chamber and the amount of infrared light without deep lung air in the sample chamber. The ethanol particulate matter is supposed to absorb the particular infrared light used in the BAC Datamaster. Generally, the process is somewhat similar to shining a flashlight against a wall and measuring the difference between the light on the wall when an object obstructs the beam of light and without an object obstructing the light.

There are countless reasons or facts that may undermine the accuracy of a breath test. This is true even if the BAC Datamaster is working properly. For example, the infrared light used in the BAC datamaster may be absorbed by other chemicals on the breath—those that have carbon-hydrogen bonds. Therefore, substances such a toluene from paints or stains, isopropanol from rubbing alcohol, or acetone that is typically found on exhaled breath may be read by the BAC datamaster. Such factors may give a false high alcohol reading. The amount of breath breathed into the sample chamber may also provide a false high alcohol reading. A sample only requires a 5 seconds or 1.5 liters of breath. However, officers will instruct a person to blow beyond 5 seconds. This will cause more breath to enter the sample chamber thereby providing a higher reading of alcohol than one who blows for a shorter period of time. Other human factors that may elevate a breath test result for reasons other than alcohol include breath temperature, breath volume, breathing pattern, alcohol in the mouth (as opposed to deep lung air), etc. Beyond this, the Washington State Patrol will also admit that there is a “confidence interval” or range of uncertainty. This confidence interval is important because (1) it shows the breath test result provided by the BAC Datamaster is in doubt; (2) the BAC Datamaster is not exact; and (3) the actual breath alcohol concentration may truly be lower. Moreover, the Washington State Patrol’s confidence interval does not take into consideration many of the human factors discussed above. In short there are countless reasons that may enable defense counsel to argue that a breath test reading is inaccurate and too high.

Contact the DUI defense attorneys at Platt & Buescher today to talk about resolving your DUI charge. The DUI attorneys at Platt & Buescher serve Oak Harbor, Island County, Bellingham, Burlington, Mt. Vernon, Whatcom County, Skagit County, Seattle, King County, and greater western Washington.