DUI Testing in Georgia

When Georgia law enforcement stops you for a suspected DUI, officers use a sequence of tests to build their case: field sobriety tests, a portable breath test (PBT) roadside, and then — after arrest — an official breath test on an Intoxilyzer 9000 or a blood draw. Each of these tests has specific legal requirements, scientific limitations, and established failure points. At Willis Law Firm, we challenge all of them.

Field Sobriety Tests (FSTs)

The National Highway Traffic Safety Administration (NHTSA) has approved three standardized field sobriety tests: the Horizontal Gaze Nystagmus (HGN) test, the Walk-and-Turn test, and the One-Leg Stand test. These tests are only valid — and only legally admissible — when administered in strict accordance with NHTSA protocol. Deviation from protocol by the arresting officer is grounds for suppression or weight challenge.

Common FST challenges: improper lighting conditions; uneven terrain; failure to properly instruct the subject; pre-existing medical conditions (inner ear disorders, knee/leg injuries, obesity, age); footwear issues; and officer failure to account for environmental conditions.

Breath Testing — Intoxilyzer 9000

Georgia uses the Intoxilyzer 9000 (I-9000) as its official evidentiary breath testing instrument. The machine measures the concentration of alcohol in a deep-lung air sample and extrapolates a blood alcohol concentration (BAC). This process involves a 2100:1 partition ratio assumption — that blood contains 2,100 times more alcohol than the same volume of breath. This ratio varies significantly between individuals, meaning the machine’s output is a statistical estimate, not a precise measurement of your actual BAC.

Breath test challenges: machine calibration and maintenance records (required to be kept and discoverable); operator certification; radio frequency interference; mouth alcohol contamination (from GERD, belching, dental work); medical conditions affecting partition ratio; failure to observe the required 20-minute deprivation period before testing.

Blood Testing — Chain of Custody & Protocol

Blood draw evidence in a Georgia DUI case is governed by O.C.G.A. § 40-6-392. The blood must be drawn by a qualified person (physician, registered nurse, certified phlebotomist, or law enforcement officer trained for this purpose) using approved equipment. Willis Law Firm has developed extensive expertise in blood draw protocol challenges, including:

• TriTech BU-3 kit requirements — the standard Georgia DUI blood draw kit uses specific vacutainer tubes containing sodium fluoride (NaF) as a preservative and potassium oxalate as an anticoagulant
• Inversion protocol — the gray-top BD Vacutainer tubes used in Georgia DUI blood draws require 8–10 complete inversions immediately after collection to ensure proper mixing with the preservative. Failure to properly invert creates conditions for fermentation and an artificially elevated BAC reading
• Chain of custody — every person who handled the sample from draw to analysis must be documented; gaps in the chain create reasonable doubt about sample integrity
• Laboratory analysis standards — the GBI Crime Lab uses gas chromatography; challenges include calibration standards, reagent quality, analyst certification, and duplicate testing requirements

The Manning Order — New Precedent for Blood Draw Cases

In March 2026, Greg Willis obtained the Manning Order from Cobb County State Court, declaring O.C.G.A. § 40-6-392(d) unconstitutional as applied under the Fourth Amendment to the U.S. Constitution and Article I, Section I, Paragraph XIII of the Georgia Constitution. This ruling has direct implications for DUI cases involving blood evidence and represents one of the most significant DUI-related constitutional rulings in Georgia in years.

Implied Consent — Your Rights When Asked to Test

Georgia’s implied consent law requires officers to read a specific implied consent notice before requesting chemical testing. A 2019 Georgia Supreme Court ruling won by Greg Willis established that forcing a driver to submit to a breath test — or using refusal as evidence of guilt — raises serious constitutional concerns. That ruling continues to shape how implied consent is applied in Georgia courts.