Challenging the DUI Breath Tests in Georgia based on the Codified 2100:1 Blood-Breath Partition Ratio in Georgia DUI Cases: Is it a DUI Breath Test or a DUI Breath Guess

As a seasoned DUI attorney in Georgia, I’ve seen firsthand how supposedly scientific breath tests can make or break a case. Recently, in a DUI motion hearing, Chris Tilson, head of the Georgia Bureau of Investigation’s Toxicology Section, testified that the Georgia legislature has codified the 1:2100 blood-breath partition ratio (BBR) directly into the definition of “alcohol concentration.” He argued that it doesn’t matter if breath alcohol levels could be twice the blood alcohol concentration (BAC) during the pre-peak blood alcohol absorption phase because the statutory definition equates grams of alcohol per 100 milliliters of blood to grams of alcohol per 210 liters of breath. This codification, he suggested, renders scientific variability irrelevant. But as we’ll explore, the science tells a different story—one that could be crucial for defending clients in DUI prosecutions.

The Statutory Foundation Of Alcohol Concentration: O.C.G.A. § 40-1-1(1) And Its Implications

In Georgia, the law defines “alcohol concentration” as “grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath.” O.C.G.A. § 40-1-1(1) (2024). This language effectively codifies as law the blood breath partition ratio of 2100:1, assuming that 210 liters of breath contain the same amount of alcohol as 100 milliliters of blood. This equivalence underpins per se DUI violations under O.C.G.A. § 40-6-391(a)(5), where a reading of 0.08 grams or higher can lead to conviction without further proof of impairment.

Georgia courts have historically upheld this approach, ruling that the legislature’s definition eliminates the need for individual conversion or challenges to the ratio. For example, in Lattarulo v. State, 261 Ga. 124, 401 S.E.2d 516 (1991), the Georgia Supreme Court held that breath test results are scientifically reliable under a Harper and Frye analysis. Similarly, in Campbell v. State, 248 Ga. App. 162, 545 SE 2d 6 (2001), the Court of Appeals rejected jury charges regarding Blood Breath Ratio variability reinforcing the statutory presumption and limiting defenses based on individual physiological differences.

Tilson’s testimony echoes this view, emphasizing that the codified ratio makes pre-peak discrepancies (where breath readings may overestimate BAC during alcohol absorption) legally moot. However, with Georgia’s adoption of the Daubert standard for expert testimony in criminal cases via House Bill 478 (effective July 1, 2022, amending O.C.G.A. § 24-7-702), we now have a stronger framework to scrutinize the scientific reliability of breath tests. Under Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), courts must evaluate whether expert methods are testable, peer-reviewed, have known error rates, and are generally accepted—factors that could open the door to challenging the uniform application of the 2100:1 ratio.

The Science: Factors Influencing Blood-Breath Partition Ratio Variability

Despite the statutory codification, scientific studies demonstrate that the Blood Breath Ratio is not a fixed 2100:1 for everyone—or even for the same person under different conditions or during the same continuous blow. Variability can lead to inaccurate Blood Alcohol and Breath Alcohol Content estimates from breath tests, potentially resulting in over-estimations and under-estimates that unfairly prejudice defendants and violate Equal Protection standards. Here are key factors supported by peer-reviewed research:

1. Absorption Phase and Arterial-Venous Differences: During the absorption phase (pre-peak, shortly after drinking), arterial BAC is higher than venous BAC, leading to elevated breath alcohol concentrations (BrAC) that may not accurately reflect true BAC. This can cause BrAC to be up to twice the BAC, as Tilson acknowledged, but studies show this variability undermines the fixed ratio’s reliability.
2. Body and Breath Temperature: Higher temperatures decrease the BBR, as ethanol becomes more volatile and partitions more into breath. Research indicates a negative correlation (e.g., r = -0.324 for body temperature), with a 6.5% increase in breath alcohol per 1°C rise. Fever or environmental factors can thus skew results.
3. Breathing Patterns and Exhalation Dynamics: Hyperventilation lowers BrAC, while hypoventilation raises it. Longer exhalations approach a more stable ratio, but short breaths can inflate readings. Recent studies suggest the ratio changes during a single exhalation, from lower to higher as breath progresses.
4. Hematocrit Levels and Blood Composition: Higher hematocrit (red blood cell proportion) reduces blood water content, where alcohol dissolves, leading to higher BrAC for the same BAC. Gender differences (men typically 40-54%, women 36-47%) contribute here.
5. Individual Physiological Variations: Studies of hundreds of subjects show BBR ranges from 1706:1 to 3063:1, far from a constant 2100:1. A 2006 study of 402 volunteers found some with zero BrAC despite positive BAC, highlighting extreme variability. Overall, high correlations exist between BrAC and BAC (r = 0.983), but individual deviations can be significant.

These factors are not hypothetical; they’re documented in forensic toxicology literature, challenging the assumption that a uniform ratio applies reliably across all defendants.

Opportunities For Challenge In Georgia DUI Defenses

Pre-Daubert cases like Lattarulo and Campbell shut down BBR variability arguments, but the 2022 amendment to O.C.G.A. § 24-7-702 now requires courts to apply Daubert’s rigorous scrutiny to scientific evidence in criminal matters, including breath tests. This shift, as seen in Trial Court motions, allows defense attorneys to file Daubert motions to exclude unreliable breath results. We argue that the state’s breath test fail Daubert’s criteria for methodology, peer review, error rates, and general acceptance.

If you’re facing a DUI charge in Georgia, don’t assume a breath test reading is ironclad. It is more of a breath guess than a breath test since the Government has codified a variable factor in the DUI statute. Factors like those above could form the basis of a strong scientific challenge, especially if we can introduce expert testimony showing your individual BBR deviates from 2100:1. Courts may now be more receptive, given Daubert’s emphasis on reliability over mere statutory presumption.

At George C. Creal, Jr. P.C., Trial Lawyers we specialize in dissecting these scientific and legal nuances to protect your rights. If you’ve been arrested for DUI, contact us today for a free consultation. Remember, this post is for informational purposes only and not legal advice—laws evolve, so always check current sources or consult an attorney for your specific situation.