As a seasoned Atlanta DUI attorney, I am committed to staying informed about scientific advancements that impact DUI defense. A recent study, “The Alcohol Breath Test in Practice: Effects of Exhaled Volume” by Joseph C. Anderson and Michael P. Hlastala (J Appl Physiol, 126: 1630-1635, 2019), provides critical insights into the limitations of alcohol breath tests (ABTs). This article, which I’ve carefully reviewed, highlights how exhaled breath volume affects breath alcohol concentration (BrAC) measurements, offering valuable ammunition for challenging ABT results in DUI cases. Here’s my analysis of the study and its implications for Georgia DUI defense.
Study Overview
Published in 2019, the study analyzes 115 evidentiary ABTs conducted using the Alcotest 9510 in Washington State between 2015 and 2018. The researchers examined how the volume of air exhaled during a breath test influences BrAC, which is used to estimate blood alcohol concentration (BAC) for legal purposes. The study’s key findings are based on real-world data from 230 breath samples (two per test) collected by police, with detailed measurements of exhaled flow rates and BrAC.
Key Findings
- Exhaled Volume Varies Widely: On average, subjects exhaled about 53% of their predicted vital capacity (VC), the maximum amount of air a person can exhale after a full inhalation. Most (81%) exhaled between 30% and 70% of their VC, with only 8% approaching a full VC. Duplicate breath samples typically had similar volumes, likely due to feedback from the Alcotest 9510’s display, which guides officers to match the second sample to the first.
- BrAC Increases With Exhaled Volume: The study found that BrAC rises as more air is exhaled, at an average rate of 9.2 ± 2.8% per liter beyond the minimum required volume (1.5 liters in Washington). This is because ethanol, a highly blood-soluble compound, primarily exchanges in the lung’s airways, not the alveoli, contrary to outdated assumptions. As exhalation continues, less alcohol is deposited on the airway walls, increasing the measured BrAC.
- Bias In Testing: Subjects who exhale just beyond the minimum volume (e.g., 1.6 liters) have a lower BrAC than those who exhale closer to their full VC, even if their BAC is identical. This variability can lead to a BrAC difference of up to 40%, depending on lung capacity and effort. Conversely, individuals with smaller lung volumes face a bias, as they must exhale a larger percentage of their VC to meet the minimum, potentially inflating their BrAC.
- Device Discrepancies: Alarmingly, the BrAC printed on the breath test ticket (used for legal purposes) was higher than the end-exhaled BrAC in 92% of cases, with the difference increasing at higher BrAC levels. The study notes that the Alcotest 9510’s flow sensors are not calibrated for volume, and measurements are not adjusted to standard body temperature and pressure conditions, adding further uncertainty.
Implications For DUI Defense
This study is a goldmine for DUI defense attorneys in Georgia, where breath tests like those using the Intoxilyzer 9000 are common. The findings expose significant flaws in ABT reliability, which can be leveraged to challenge evidence in court:
- Challenging BrAC Accuracy: The increase in BrAC with exhaled volume means that test results are heavily influenced by how much air a defendant exhales, not just their actual BAC. If a client exhaled more than the minimum volume, their BrAC may be artificially inflated, providing grounds to question the test’s validity.
- Highlighting Bias: The study shows that cooperative defendants who follow instructions to “keep blowing” may face higher BrAC readings, while those with smaller lung capacities are disadvantaged by needing to exhale a larger fraction of their VC. These biases can be used to argue unfairness in the testing process.
- Questioning Device Calibration: The lack of volume calibration and failure to adjust for thermodynamic conditions (e.g., breath temperature) undermines the precision of ABT devices. In Georgia, where the Intoxilyzer 9000 has its own calibration protocols, similar issues may exist, warranting expert testimony to challenge the device’s reliability.
- Discrepancies in Reported BrAC: The finding that ticketed BrAC values often exceed actual end-exhaled BrAC suggests potential errors in how results are recorded or processed. This discrepancy can be a critical point in suppressing breath test evidence or casting doubt on its accuracy.
Strategic Applications In Georgia DUI Cases
At the Law Office of George C. Creal, Jr. P.C., we use scientific evidence like this to build robust defenses. The Anderson and Hlastala study aligns with strategies we employ to contest ABT results in Georgia DUI cases:
- Motion To Suppress: We can argue that BrAC results are unreliable due to variability in exhaled volume, especially if the defendant’s lung capacity or breathing effort was not considered. This is particularly relevant in cases where the BrAC is close to the legal limit (0.08 g/210 liters in Georgia).
- Expert Testimony: Engaging a forensic toxicologist to explain airway exchange and the impact of exhaled volume can help jurors understand why ABT results may not accurately reflect BAC, especially in cases involving medical conditions like asthma or COPD that affect lung capacity.
- Cross-Examination Of Officers: The study’s note about officer coaching and device feedback suggests that breath samples may not be independent. We can question officers about their instructions and the device’s influence on exhaled volume to highlight procedural flaws.
Why This Matters For You
If you’re facing a DUI charge in Georgia, understanding the science behind breath tests is crucial. The Anderson and Hlastala study reveals that ABTs are not as foolproof as prosecutors claim. Factors like exhaled volume, lung capacity, and device calibration can significantly skew results, potentially leading to wrongful convictions. As an experienced DUI lawyer, I know how to use this science to challenge evidence and protect your rights.
Contact Us For Expert DUI Defense
With over 25 years of experience, the Law Office of George C. Creal, Jr. P.C. is dedicated to fighting DUI charges with cutting-edge legal and scientific strategies. If you’ve been charged with a DUI in Atlanta or anywhere in Georgia, don’t let flawed breath test evidence define your case. Contact us today at (770)-961-5511 or visit www.georgialawyer.com for a free consultation. Let us put our expertise to work for you.
