Field sobriety tests (FSTs) are a routine component of DUI investigations in Georgia, used by law enforcement officers to assess whether a driver is impaired by alcohol or drugs. While these tests are widely administered and frequently cited by prosecutors, they are not infallible, they are not required by Georgia statute, and their reliability has been the subject of significant legal and scientific debate. Understanding how these tests work, how they are scored, and where they fail is critical to mounting an effective DUI defense.

No Statutory Requirement for Specific Tests

Georgia law does not mandate that any particular field sobriety test be administered during a DUI investigation. There is no statute specifying which tests an officer must use, nor any prohibition on an officer using non-standardized tests of their own devising. This is a significant legal reality that defense attorneys regularly address: because the law imposes no specific requirements, officers have wide discretion — and defense counsel must carefully examine whether the tests actually administered are validated, properly administered, and correctly interpreted.

A person stopped by law enforcement in Georgia is not legally required to perform field sobriety tests. FSTs are voluntary, and refusal to perform them generally cannot be used as direct evidence of guilt. However, officers may use the refusal as one factor in their probable cause determination, and the interaction leading up to and following a refusal will still be captured on video and potentially used in a prosecution.

The Three Standardized Field Sobriety Tests

The National Highway Traffic Safety Administration (NHTSA) has validated three specific field sobriety tests as reliable indicators of alcohol impairment when properly administered. These are the only tests that have been scientifically validated for this purpose, and Georgia law enforcement agencies train officers to administer them pursuant to NHTSA standards. Deviation from those standards undermines the reliability — and therefore the admissibility and evidentiary weight — of the results.

1. Horizontal Gaze Nystagmus (HGN)

The horizontal gaze nystagmus test is considered the most reliable of the three standardized field sobriety tests, with NHTSA studies suggesting a correlation with blood alcohol concentration at or above 0.08 when properly administered. Nystagmus is an involuntary jerking of the eyes. Alcohol and certain other substances affect the central nervous system in a way that causes nystagmus to onset at a smaller angle of gaze and to become more pronounced at maximum deviation.

During the HGN test, the officer holds a stimulus — typically a pen, penlight, or fingertip — approximately 12 to 15 inches from the suspect’s nose and moves it slowly from side to side. The officer is evaluating for three clues in each eye: lack of smooth pursuit (the eye jerks or bounces instead of following smoothly), distinct nystagmus at maximum deviation (the eye jerks visibly when moved as far as possible to the side), and onset of nystagmus prior to 45 degrees of gaze.

The HGN test must be administered in accordance with NHTSA standards to be scientifically reliable. Officers must ensure adequate lighting, instruct the subject to remove contact lenses if worn, hold the stimulus at the correct height and distance, and move it at the correct speed. Defense attorneys routinely challenge HGN results when dashcam footage reveals deviations from protocol, or when the officer lacked proper training in administering the test.

2. Walk-and-Turn Test

The walk-and-turn test is a divided-attention test that requires the subject to listen to and follow instructions while simultaneously performing a physical task. The officer instructs the subject to stand with feet in a heel-to-toe position, arms at their sides, while receiving instructions — the instruction phase itself is a clue-gathering opportunity, as officers observe whether the subject can maintain the starting position.

The walking phase requires the subject to take nine heel-to-toe steps along a real or imaginary line, turn using a series of small steps while keeping the front foot on the line, and walk nine heel-to-toe steps back. Officers score the test by counting the number of clues observed from eight possible indicators: starting too soon, stopping while walking, failing to touch heel-to-toe, stepping off the line, using arms for balance, making an improper turn, taking the wrong number of steps, and inability to maintain the instructed stance during the instruction phase.

According to NHTSA, observing two or more clues on the walk-and-turn test indicates a likelihood of a BAC at or above 0.08 in approximately 79 percent of cases. Defense counsel examines the surface on which the test was administered (uneven, sloped, or gravel-covered surfaces affect performance), the subject’s footwear, any physical conditions affecting balance, and whether the officer properly demonstrated the test.

3. One-Leg Stand Test

The one-leg stand test requires the subject to stand on one foot with the other foot approximately six inches off the ground, arms at their sides, while counting aloud by thousands (one-one-thousand, two-one-thousand, etc.) until told to stop — typically for 30 seconds. Officers score the test by counting clues from four possible indicators: swaying while balancing, using arms to balance, hopping to maintain balance, and putting the raised foot down.

NHTSA reports that two or more clues on the one-leg stand test indicate a likelihood of a BAC at or above 0.08 in approximately 83 percent of cases. However, individuals over the age of 65, those more than 50 pounds overweight, or those with inner ear problems, back injuries, leg injuries, or other physical conditions that affect balance may perform poorly on this test for reasons entirely unrelated to alcohol consumption. Defense counsel consistently challenges the one-leg stand results where any such factors are present.

The Romberg Balance Test

Though less commonly administered than the three NHTSA-standardized tests, officers occasionally use the Romberg balance test — or a modified version of it — during DUI investigations, particularly in DUI-drugs cases. The test requires the subject to stand with feet together, tilt the head slightly back, close their eyes, and estimate the passage of 30 seconds internally, then open their eyes and say ‘stop.’

The officer is evaluating for sway (forward, back, or circular), eyelid tremors, muscle tremors, and the accuracy of the subject’s internal time estimate. A person who significantly overestimates or underestimates 30 seconds is deemed to show signs of impairment. The Romberg test is frequently used by Drug Recognition Experts (DREs) as part of a 12-step evaluation, but its scientific validity as a standalone indicator of impairment is less firmly established than the three NHTSA-standardized tests.

Challenging Field Sobriety Test Results in Court

Field sobriety tests are not pass/fail examinations with objective scores. They are subjective assessments made by an officer who has already formed an opinion about the driver’s impairment before the tests even begin. Officers observe and record only the clues they are trained to look for — and dashcam footage, when available, frequently tells a different story than the officer’s written report.

Defense attorneys in Georgia regularly challenge field sobriety test results by demonstrating improper administration, inadequate training of the administering officer, environmental conditions that compromised performance, physical or medical conditions of the defendant that explain poor performance, and the inherently subjective nature of the scoring. The Georgia Court of Appeals has recognized that improperly administered field sobriety tests may be challenged for admissibility and reliability.