BAC Test Errors in Georgia DUI Cases: A Defense Lawyer's Breakdown

Most Georgia DUI cases come down to a single number on a chemical test printout — and most chemical tests have weak points if you know exactly where to look. After three decades defending DUI cases across Atlanta, I've seen the same procedural failures surface in case after case. This is a technical breakdown of where BAC evidence breaks down in Georgia, written for clients who want to understand what their defense lawyer is actually looking for in the discovery file. If you're new to the topic, start with our Georgia BAC limit guide — this article goes deeper into the science.

The Intoxilyzer 9000: How Georgia Tests Breath

Most Georgia agencies use the Intoxilyzer 9000, manufactured by CMI, Inc. It's a desktop breath testing device that measures alcohol in deep lung air using infrared spectroscopy. The result is reported as a blood alcohol concentration — but the machine never actually measures blood. It measures breath and converts it using a standardized ratio (2,100 parts breath to 1 part blood) that doesn't apply equally to every human body. That ratio alone introduces a real margin of error.

The device requires a strict pre-test protocol: a 20-minute deprivation period, a working internal standard, two sequential breath samples, and a tolerance check between the two readings. If any step is skipped or documented incorrectly, the result is vulnerable to a suppression motion. Reviews of Georgia DUI cases consistently find roughly 1 in 4 chemical tests showing measurable procedural errors. That's not a hypothetical defense — it's the baseline reality of breath testing in this state.

Calibration and Maintenance Log Failures

Every Intoxilyzer 9000 in Georgia must be calibrated and inspected on a regular cycle, with each procedure logged in the device's maintenance records. The state has the burden of producing these records on request. When they can't — or when the records show gaps, late inspections, or unexplained anomalies — the BAC result becomes vulnerable.

Things I look for in every Intoxilyzer maintenance log: the dates of the most recent calibration before and after the test, the operator who performed the calibration, any error codes the machine logged in the preceding 30 days, and whether the device was taken out of service for repair without proper requalification. A single gap in this paper trail can be enough to argue that the result is unreliable.

The 20-Minute Observation Rule

Before administering a breath test, the officer is required to continuously observe the suspect for 20 minutes. The purpose is to rule out mouth alcohol contamination from burping, regurgitation, vomiting, or anything entering the mouth — all of which can produce a falsely elevated BAC reading. Continuous observation means exactly that: eyes on the suspect for the entire period.

In practice, the 20-minute observation is one of the most commonly violated rules in DUI procedure. Officers turn away to write reports, complete paperwork, or speak with backup. Body camera footage frequently shows interruptions that weren't documented in the arrest report. When the footage contradicts the officer's testimony, the test result is vulnerable to exclusion.

Mouth Alcohol Contamination

Mouth alcohol — alcohol that lingers in the mouth, throat, or esophagus — can cause a breath testing device to report a BAC several times higher than the actual blood concentration. Common sources include recent drinking (within the last 20 minutes), dental work that traps liquid, the use of mouthwash or breath spray, and gastroesophageal reflux (GERD), which can push stomach contents back into the throat unnoticed.

If the breath test was administered shortly after the last drink, or if my client has a documented history of GERD, that's a real defense angle. Medical records and the timing reconstruction from body camera footage are both critical pieces of evidence here.

Blood Tests: Chain of Custody Issues

When a blood draw is taken — typically in high-BAC cases, accidents involving injury, or refusal cases where the state seeks a warrant — the chain of custody becomes the focal point of the defense. From the moment the blood is drawn, every person who touches the vial must be documented: the medical technician who drew the sample, the officer who took possession, the evidence room where it was stored, the lab where it was tested.

Blood samples are also subject to fermentation. If the sample is not properly preserved with the correct anticoagulant and refrigerated promptly, microbial growth can produce alcohol inside the tube — generating a falsely elevated BAC result that has nothing to do with what was actually in the bloodstream at the time of the draw. Reviewing the lab's storage logs and the timeline between draw and test is standard work in any blood-test DUI case.

Operator Certification Gaps

Only operators certified by the Georgia Bureau of Investigation may administer the Intoxilyzer 9000. Certifications expire and must be renewed; if the test was administered by an officer with a lapsed certification, the result is inadmissible. I routinely request the operator's certification records as part of the standard discovery in every breath-test DUI case. Lapses are uncommon but not rare — and when they happen, the case can fall apart on a single motion.

What This Means for Your Case

If you've been arrested for DUI in Georgia with a chemical test result, the BAC number on your discovery file is not necessarily what a jury will see. Every challenge described above starts with a careful review of the arrest report, the body camera footage, the Intoxilyzer maintenance log, and the operator's certification records. The earlier that review happens, the more options are still available — including the 30-day window to appeal the administrative license suspension.

For a step-by-step breakdown of how each BAC level affects your case under Georgia law, see our Georgia BAC limit guide. For an immediate confidential review of your specific arrest, call (770) 419-1945 — consultations are free, available 24/7 for DUI emergencies.