After a traffic stop where the officer suspects impairment, you will likely be asked to step out of your vehicle and perform field sobriety tests. These tests feel official and mandatory. They are not. Understanding what each test measures, how unreliable they are, and what happens when you refuse is essential information for anyone stopped under suspicion of DUI in Utah.
The Three Standardized Tests
Law enforcement uses three tests developed and validated by the National Highway Traffic Safety Administration (NHTSA): the Horizontal Gaze Nystagmus test, the Walk-and-Turn, and the One-Leg Stand. These are the only field sobriety tests with any scientific backing, and even that backing has significant limitations. Non-standardized tests — reciting the alphabet, counting backwards, touching your nose — have no validated correlation to impairment and are challenged more easily in court.
Horizontal Gaze Nystagmus (HGN)
The officer holds an object in front of your face and moves it side to side, watching your eyes track the movement. Nystagmus — an involuntary jerking of the eye — occurs naturally at the extremes of gaze, but alcohol causes it to appear earlier and more pronounced. Officers look for six clues: lack of smooth pursuit in each eye, distinct nystagmus at maximum deviation in each eye, and onset of nystagmus prior to 45 degrees in each eye. NHTSA's research suggests that four or more clues indicate a BAC at or above 0.08 approximately 77 percent of the time.
Utah's DUI threshold is 0.05 BAC under Utah Code § 41-6a-502 — lower than the federal standard used in the NHTSA research. The HGN validation studies were not conducted at 0.05. This creates a legitimate challenge to HGN results in Utah DUI cases.
Walk-and-Turn
You are asked to take nine heel-to-toe steps along a straight line, turn in a specific manner, and walk back nine heel-to-toe steps. Officers look for eight clues including loss of balance during instructions, starting too soon, stopping while walking, missing heel-to-toe contact, stepping off the line, using arms for balance, turning incorrectly, and taking the wrong number of steps. Two or more clues are considered indicative of impairment above 0.08 BAC approximately 68 percent of the time under NHTSA research.
The test requires a reasonably dry, level, non-slippery surface. Footwear, age, weight, pre-existing leg or inner ear conditions, and even nervousness can affect performance. These factors are all challengeable.
One-Leg Stand
You are asked to raise one foot approximately six inches off the ground and hold the position while counting aloud for thirty seconds. Officers look for four clues: swaying, using arms for balance, hopping, and putting the foot down. Two or more clues are considered indicative of impairment above 0.08 BAC approximately 65 percent of the time under NHTSA research.
The same physical limitations that affect the Walk-and-Turn affect the One-Leg Stand. Anyone over 65, anyone with leg, back, or inner ear problems, and anyone more than 50 pounds overweight may be unable to perform this test regardless of sobriety.
These tests are not pass/fail in the everyday sense. Officers are scoring them, but the scoring is subjective, the training varies, and the conditions are rarely ideal. Body camera footage, dashcam footage, and cross-examination of the officer's administration technique frequently reveal problems with how tests were conducted.
Are You Required to Take Field Sobriety Tests in Utah?
No. Utah's implied consent statute, Utah Code § 41-6a-520, requires you to submit to a chemical test — breath, blood, or urine — after a lawful arrest for DUI. It does not require you to perform roadside field sobriety tests before an arrest.
Declining to perform field sobriety tests carries no automatic administrative license suspension. The officer can still arrest you based on other indicators of impairment, and your refusal can be mentioned at trial — but you have not provided the prosecution with video evidence of your performance on the tests.
The Tradeoff Is Real
If you decline the tests, the officer will likely arrest you anyway if there are other indicators of impairment. Your refusal may be presented to a jury as circumstantial evidence of consciousness of guilt, though a skilled attorney can address this argument effectively.
If you perform the tests, the results — including every stumble, pause, or touch — are captured on video and become evidence against you. There is no version of the field sobriety tests that helps you. They exist to build the officer's probable cause and the prosecutor's case.
The Portable Breath Test
Before a formal arrest, officers often ask you to blow into a handheld breathalyzer at the roadside. This device — sometimes called a preliminary breath test or PBT — is typically not subject to the same calibration and certification standards as the instruments used at the station. In Utah, you are generally not required to submit to a roadside PBT before arrest, and refusal does not trigger the automatic license suspension that follows refusal of the post-arrest chemical test.
Results from a roadside PBT are often not admissible at trial for the specific BAC reading, though they may be used to establish probable cause for the arrest itself.
If You Performed the Tests
If you already performed the tests and were arrested, that is not the end of the road. The administration of the tests can be challenged. Dashcam and body camera footage frequently reveals that officers gave incomplete instructions, failed to demonstrate the tests properly, or scored clues incorrectly. Pre-existing conditions affecting your balance or gaze can be introduced as alternative explanations. The validity of the NHTSA research as applied to Utah's 0.05 BAC standard is itself a legitimate area of challenge.
Contact a DUI defense attorney as soon as possible. Do not wait to see what happens.
DUI Arrest in Utah? Your Defense Starts Now.
Jim Tily handles DUI defense throughout Utah, including challenging field sobriety test results. Free consultations. Call today.
(801) 641-0883 Send a MessageThis article is for general informational purposes only and does not constitute legal advice. Laws change and individual circumstances vary. Contact an attorney to discuss your specific situation.