Challenging Breath Test Results

Posted on June 12, 2023 in Uncategorized

By Eric H. Sills, Esq.

There are a number of challenges that can be made to the validity of a breath test result. Some of the more common are set forth below. Keep in mind that the author is from New York, which is both (a) a "one-blow" State, and (b) a blood alcohol concentration ("BAC") State, not a breath alcohol concentration ("BrAC") State.

THE BLOOD/BREATH RATIO

Breath testing devices operate under the presumption that everyone has the exact same blood/breath ratio, and that this ratio never changes (i.e., Henry's Law). The presumption is that the concentration of alcohol in a person's blood is 2,100 times greater than the concentration of alcohol in the person's breath. More specifically, breath testing devices presume that the amount of alcohol that is present in 2,100 milliliters of a person's deep lung (or alveolar) air is the same as the amount of alcohol that is present in 1 milliliter of the person's blood. The machine uses this mathematical formula to convert a BrAC into a BAC.

The way that the defense can utilize the blood/breath ratio is surprisingly simple. Breath test operators ("BTOs") are trained in the basic principles of how the breath test device works. BTOs will (or should) be familiar with phrases like Henry's Law and blood/breath ratio. They will generally concede that they were trained regarding the information in the preceding paragraph, and that they were also trained that the blood/breath ratio (a) varies from person to person, (b) can even vary in the same person (at different times), and (c) changes at different body/breath temperatures (which is why the simulator solution used in connection with a breath test is required to be 34°C +/- .2°C). Since the police do not test a DUI/DWI suspect's actual blood/breath ratio, the BAC reported by a breath test device is really more of an estimate than a precise measurement.

BREATH TEMPERATURE

In addition to operating under the false presumption that everyone has the same, fixed blood/breath ratio, breath testing devices also operate under the presumption that everyone has a normal body temperature, and that the temperature of their breath at the time that they blow into the machine is 34°C (which, again, is why the simulator solution used in connection with a breath test is required to be 34°C +/- .2°C). All other factors aside, if a person's breath temperature is higher than 34°C the person's test result will be artificially high (and vice versa). Although modern breath test devices can be equipped with breath temperature sensors, New York has chosen not to pay for this option. Without knowing the subject's breath temperature, the BAC reported by a breath test device is more of an estimate than a precise measurement.

MOUTH ALCOHOL

A breath test result is only reliable if the breath being tested is "deep lung" or "alveolar" air. The amount of alcohol in alveolar air most closely approximates the amount of alcohol in the blood. It is captured by having the person blow into the machine for a period of time sufficient to exhaust the air in the person's lungs.

If the breath sample contains alcohol from a source other than the suspect's alveolar air (e.g., alcohol brought up from the stomach by a burp or as a result of GERD), the breath sample will be contaminated (and the test result will be artificially high). To reduce the risk of this happening, the New York State Department of Health requires that "[t]he subject shall be observed for at least 15 minutes prior to the collection of the breath sample, during which period the subject must not have ingested alcoholic beverages or other fluids, regurgitated, vomited, eaten, or smoked, or have placed anything in his/her mouth." 10 NYCRR § 59.5(b). Most police agencies require that the observation period be for at least 20 minutes. Many, if not most, observation periods (which are often captured on video) are arguably deficient.

Modern breath test devices are equipped with so-called "slope detectors." These are computer algorithms that are supposed to detect mouth alcohol and abort a contaminated test. In my experience, most BTOs are not sufficiently trained in the operation of the slope detector to testify competently (or persuasively) about it in Court. In fact, I've had cases where I raised a mouth alcohol defense yet the prosecution did not even mention the slope detector.

RADIO FREQUENCY INTERFERENCE ("RFI")

Most breath test devices can be affected by RFI. In addition, most breath test devices are located in police stations (and most police stations have radio transmitters). Nonetheless, many police agencies do little or no testing for RFI. In addition, although modern breath test devices are equipped with an RFI detector, most BTOs are not sufficiently trained in its operation to testify competently (or persuasively) about it in Court.

THE DEVICE MALFUNCTIONED

Pre-trial discovery can reveal the failure by a police agency to (a) have its breath test device(s) calibrated in a timely manner, (b) perform required weekly simulator tests, (c) follow departmental rules and regulations pertaining to breath testing, and/or (d) repair the device when anomalous results are obtained. While not every such failure is significant, one or more of these lapses can create doubt in jurors' minds as to whether the device malfunctioned.

THE BETTER TEST DEFENSE

Proof beyond a reasonable doubt should require that the prosecution utilize the most accurate technique available to determine a DUI/DWI suspect's BAC. A breath test is not the most accurate method of determining a person's BAC. A blood test is. Most BTOs will concede this (and will concede that breath tests are used because they are simpler and cheaper than blood tests). Thus, the prosecution's decision to use a breath test rather than a blood test can be used as a defense (especially where other defenses discussed above have been effectively utilized).

Eric H. Sills is a criminal defense attorney in Albany, New York, whose practice focuses on DWI defense. He is a partner in the law firm of Gerstenzang, Sills, Cohn & Gerstenzang and, together with Peter Gerstenzang, is the co-author of the book Handling the DWI Case in New York. Eric was named Best Lawyers' Albany DUI/DWI Defense "Lawyer of the Year" in both 2015 and 2022. Eric is Board Certified by the NCDD,* is a Co-Chair of the Alcohol & Drug Testing Devices Task Force, and was previously a Co-Chair of the Trial Advocacy Task Force.

* "This certification is not granted by any governmental authority." Rules of Prof. Conduct, Rule 7.4(c)(1). See also Hayes v. New York Attorney Grievance Comm. of the 8th Jud. Dist., 672 F.3d 158 (2d Cir. 2012).

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