Field Sobriety Tests in Utah

The Three NHTSA Standardized Field Sobriety Tests

Utah law enforcement officers use three standardized field sobriety tests developed through research funded by the National Highway Traffic Safety Administration: the Horizontal Gaze Nystagmus test, the Walk and Turn test, and the One Leg Stand test. These are the only three tests that NHTSA has validated as having a scientific basis for detecting alcohol impairment, and they are the tests that carry the most evidentiary weight in a Utah DUI case. Officers may also administer non-standardized tests such as the finger-to-nose test, the Romberg balance test, or alphabet and counting exercises, but these additional tests have no validated scientific foundation and carry less weight in court.

The Horizontal Gaze Nystagmus test measures involuntary jerking of the eye as it tracks a stimulus, usually a pen or finger, moved across the field of vision. The officer looks for three clues in each eye: lack of smooth pursuit as the eye follows the stimulus, distinct and sustained nystagmus at maximum deviation when the eye is held at the far edge, and onset of nystagmus prior to 45 degrees. A total of four or more clues out of six possible indicates impairment according to the NHTSA manual. The HGN test is considered the most reliable of the three standardized tests, but its accuracy was validated at .08 BAC, not Utah's .05 threshold.

The Walk and Turn test is a divided attention test that requires the subject to listen to instructions while maintaining a starting position, then walk nine heel-to-toe steps along a real or imaginary line, execute a specific turning sequence, and walk nine steps back. The officer scores eight possible clues: inability to maintain balance during instructions, starting too soon, stopping while walking, failure to touch heel to toe, stepping off the line, using arms for balance, improper turn, and incorrect number of steps. Two or more clues indicates impairment according to NHTSA standards.

The One Leg Stand test requires the subject to raise one foot approximately six inches off the ground and count aloud for 30 seconds while maintaining balance. The officer looks for four clues: swaying while balancing, using arms for balance, hopping, and putting the foot down. Two or more clues indicates impairment. Like the Walk and Turn, the One Leg Stand is a divided attention test that splits the subject's concentration between a physical task and a mental task simultaneously.

Accuracy Rates and Known Limitations

Field sobriety tests are presented by the prosecution as scientific evidence of impairment, but the science behind them includes significant limitations that affect their reliability. The NHTSA validation studies found the HGN test to be 77% accurate at detecting BAC of .08 or above, the Walk and Turn test to be 68% accurate, and the One Leg Stand test to be 65% accurate. When all three tests are used together, the combined accuracy reaches approximately 82% at the .08 threshold. Those numbers mean that even under ideal conditions with proper administration, these tests produce false positives in a substantial percentage of cases.

The accuracy question becomes more pointed in Utah because the validation studies were conducted at .08 BAC, not .05. No peer-reviewed research has established the reliability of standardized field sobriety tests at the .05 level. Utah officers are using tests validated for one threshold to make impairment determinations at a lower threshold, which creates a foundational reliability issue that the defense can raise in every case. This gap between the test validation and Utah's legal standard is one of the most significant defense tools available in field sobriety test challenges.

Beyond the baseline accuracy limitations, numerous factors reduce test reliability further in real-world conditions. The NHTSA manual specifies testing requirements: a reasonably level, dry, hard, non-slippery surface with adequate lighting and minimal distractions. Roadside conditions rarely meet those specifications. Uneven pavement, gravel shoulders, sloped surfaces, wind, rain, cold temperatures, passing traffic, and emergency vehicle lights all affect balance and coordination in ways that have nothing to do with alcohol consumption. Footwear is another factor: high heels, boots, sandals, and other non-flat-soled shoes affect performance on both the Walk and Turn and One Leg Stand tests. The NHTSA manual instructs officers to offer subjects the option to remove inappropriate footwear, but this instruction is often overlooked.

Medical conditions represent another category of factors that produce false indicators of impairment. Inner ear disorders affect the vestibular system, which controls balance. Back injuries, knee problems, hip conditions, and leg injuries all affect the ability to perform the Walk and Turn and One Leg Stand tests. Neurological conditions can affect eye movement in ways that mimic nystagmus. Certain medications influence coordination and balance. Age affects all three tests, as balance and coordination naturally decline over time. A person with an old knee injury may show multiple clues on the One Leg Stand test after consuming no alcohol at all.

Officer administration errors further reduce reliability. The NHTSA manual specifies exact instructions, demonstrations, and timing for each test. The HGN test requires the stimulus to be held at specific distances and moved at specific speeds. The Walk and Turn test requires the officer to demonstrate the turn correctly and give complete instructions before the subject begins. The One Leg Stand test requires the officer to clearly instruct the subject on which foot to raise and how to count. Departures from these requirements, such as giving incomplete instructions, demonstrating incorrectly, rushing the subject, or failing to ask about medical conditions before testing, all compromise the standardization that gives these tests whatever scientific validity they possess. Without standardized administration, the results are no longer standardized, and their probative value diminishes significantly.

The subjective nature of scoring adds another layer of concern. Two officers watching the same subject perform the Walk and Turn test may score different clues because the judgment calls involved in determining whether a step was truly "off the line" or whether arm movement was sufficient to constitute "using arms for balance" depend on the individual officer's perception and training. Research has shown inter-rater reliability issues with field sobriety test scoring, meaning different officers scoring the same performance will not always agree on the results. This subjectivity is particularly problematic when the scored clues are the primary basis for a probable cause determination and a DUI arrest. In Utah, where the .05 BAC limit means many arrested drivers are closer to sober than impaired, the subjective scoring of borderline clues carries even more weight because the tests are being applied at levels below their validated threshold.

How Glen Neeley Challenges Field Sobriety Evidence

Glen Neeley is SFST-certified through NHTSA-trained instructors, meaning he has completed the same standardized field sobriety testing training that law enforcement officers receive. That certification gives him the ability to evaluate officer performance against the exact standards the officer was trained to follow. When an officer deviates from the NHTSA manual, whether in the instructions given, the demonstration provided, the timing of the tests, or the scoring of clues, Glen can identify those deviations and present them as evidence that the test results are unreliable.

Dashcam and body camera footage is the most valuable tool in challenging field sobriety evidence because it provides an objective record of what actually happened during the testing. Glen reviews this footage in every DUI case, comparing the officer's written report to the video evidence. Discrepancies are common. An officer may report that the subject "failed to maintain heel-to-toe contact on steps 4, 6, and 8" when the video shows the gaps were minimal and within normal variation. An officer may score a clue for "using arms for balance" when the video shows the subject's arms barely moved from their sides. The gap between what the officer documented and what the video reveals is often the most effective tool for undermining the reliability of field sobriety evidence at trial or during pretrial negotiations.

Glen also reviews the officer's training records to verify SFST certification status and identify the last time the officer received refresher training. NHTSA recommends periodic refresher training to maintain proficiency, and officers who have not completed recent training may have developed habits that deviate from the current manual. As a board-certified DUI defense attorney through the National College for DUI Defense and an NCDD faculty member, Glen brings both the technical training and the courtroom experience needed to expose weaknesses in field sobriety evidence effectively. For more about how field sobriety tests fit into the overall DUI arrest sequence, see our page on the DUI arrest process. For information about the chemical testing that typically follows field sobriety testing, see our page on breathalyzer and chemical tests.