Kentucky DUI Field Sobriety Test

During a traffic stop in Kentucky where the officer suspects impairment, you will likely be asked to perform field sobriety tests on the roadside. These tests are not pass-or-fail in the way most people imagine — they are observational tools the officer uses to build probable cause for an arrest.

The Three Standardized Field Sobriety Tests

Kentucky law enforcement follows the National Highway Traffic Safety Administration (NHTSA) Standardized Field Sobriety Test (SFST) battery. This consists of three specific tests, each designed to measure different indicators of impairment:

Horizontal Gaze Nystagmus (HGN)

The officer holds a stimulus — usually a pen or small flashlight — about 12 to 15 inches from your face and asks you to follow it with your eyes while keeping your head still. The officer is watching for involuntary jerking of the eyeball (nystagmus) as your gaze moves to the side.

Three clues are evaluated per eye, for a total of six possible clues:

• Lack of smooth pursuit as the eye tracks the stimulus
• Distinct and sustained nystagmus at maximum deviation (when the eye is looking as far to the side as possible)
• Onset of nystagmus before 45 degrees

NHTSA training materials indicate that four or more clues suggest a BAC of 0.08% or higher. This test is considered the most reliable of the three — but it is also the one the driver has the least control over, since nystagmus is an involuntary physiological response.

Walk-and-Turn

The officer instructs you to take nine heel-to-toe steps along a straight line, turn in a specific manner, and take nine heel-to-toe steps back. You must keep your arms at your sides, watch your feet, and count each step aloud.

The officer scores eight possible clues:

• Cannot keep balance during instructions
• Starts before told to begin
• Stops while walking
• Does not touch heel to toe
• Steps off the line
• Uses arms for balance
• Improper turn
• Wrong number of steps

Two or more clues is classified as a failure. Environmental factors — uneven pavement, poor lighting, footwear, age, weight, and medical conditions affecting balance — can all produce clues that have nothing to do with alcohol consumption.

One-Leg Stand

The officer asks you to raise one foot approximately six inches off the ground, keep both legs straight, look at the raised foot, and count aloud ("one thousand and one, one thousand and two...") for 30 seconds.

Four clues are evaluated:

• Swaying while balancing
• Using arms for balance
• Hopping
• Putting the foot down

Two or more clues is classified as a failure. Like the walk-and-turn, this test is heavily influenced by physical condition, age, footwear, and the surface you are standing on.

Are Field Sobriety Tests Mandatory in Kentucky?

Field sobriety tests are voluntary. Kentucky's implied consent law applies to chemical tests of breath, blood, or urine administered after arrest — not to the roadside field sobriety tests that happen before arrest.

You have the legal right to decline field sobriety tests without triggering the implied consent refusal penalties (pretrial license suspension, aggravated sentencing track). However, the officer can still arrest you based on other observations: odor of alcohol, slurred speech, bloodshot eyes, erratic driving, and your performance during the initial conversation.

In practical terms, declining field sobriety tests removes a source of evidence that the prosecution would otherwise use at trial. It also removes a chance for you to demonstrate sobriety. The decision involves tradeoffs that depend on your actual condition and the specific circumstances of the stop.

How Field Sobriety Test Results Are Used in Court

Field sobriety test results serve two purposes in a Kentucky DUI case:

Establishing probable cause for arrest. The officer uses the test results, combined with other observations, to decide whether there is sufficient basis to arrest you and request a chemical test at the station. If the arrest lacked probable cause, the defense can file a motion to suppress the chemical test results.

Evidence at trial. If the case goes to trial, the prosecution presents the field sobriety test results as evidence of impairment. The officer will testify about the specific clues observed during each test.

Defense attorneys frequently challenge field sobriety test evidence on procedural grounds — whether the tests were administered according to NHTSA protocol, whether the testing conditions were suitable (level surface, adequate lighting, reasonable weather), and whether the officer's training and certification are current.

What This Means for Your Case

Field sobriety tests are one piece of a larger evidence puzzle. They are not the sole basis for a DUI conviction, and poor performance on these tests does not automatically mean your case is unwinnable. The chemical test result (breath or blood BAC), the officer's observations, and any video footage all factor into the prosecution's case.

If you are facing a first-offense DUI charge in Kentucky and have questions about the evidence in your case, the Kentucky First-Offense DUI Guide breaks down the entire process from the initial traffic stop through court proceedings and license reinstatement.

See more Kentucky guides →