The one-leg stand field sobriety test is a roadside balance exercise in which you raise one foot about six inches off the ground, keep it parallel to the surface, and count aloud (“one thousand one, one thousand two…”) for 30 seconds while a trained officer watches for signs of impairment. It’s one of the three tests in the Standardized Field Sobriety Test battery developed with funding from the National Highway Traffic Safety Administration, and when administered by the book it is 83% accurate at identifying drivers at or above a 0.08 blood alcohol concentration.1National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Participant Manual The accuracy figure assumes the officer follows the standardized protocol exactly, and deviations are where most courtroom challenges start.
How the Test Is Performed
The test runs in two stages, and the officer is scoring you during both.
In the instruction phase, you’re told to stand with feet together and arms at your sides. The officer demonstrates the stance, explains that you’ll be raising one leg about six inches off the ground with the foot parallel to the surface, legs straight, arms down, counting aloud until told to stop. The officer must demonstrate the count and the leg raise, and must ask whether you understand before giving the command to begin.1National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Participant Manual Starting early, swaying, or breaking the stance during this phase can itself be noted. People who are impaired often struggle to hold still and listen at the same time, which is exactly what this stage is designed to reveal.
Once you confirm you understand, you pick which foot to raise, lift it about six inches, stare at it, and count out loud. The officer times the full exercise at 30 seconds using a watch or similar device.2National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Refresher Instructor Guide Thirty seconds doesn’t sound long until you try it. Balancing on one leg while keeping your eyes fixed down, holding your arms still, and counting in a steady cadence puts enough load on the brain to expose the coordination problems alcohol causes.
The Four Clues Officers Score
Officers look for exactly four indicators during the 30 seconds. Each one counts as a single clue no matter how many times it occurs.
- Swaying while balancing — a persistent side-to-side or back-and-forth shift in your center of gravity, not minor natural tremor.2National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Refresher Instructor Guide
- Using arms for balance — moving your arms six or more inches from your sides.2National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Refresher Instructor Guide
- Hopping — jumping on the standing foot to keep from falling. One hop or ten, it’s one clue.2National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Refresher Instructor Guide
- Putting the foot down before the 30 seconds are up. The officer should tell you to pick it back up and continue counting from where you left off.2National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Refresher Instructor Guide
If you can’t complete the test — you give up, fall, or put your foot down repeatedly — the officer records whatever clues were observed and notes why it ended early. Inability to finish carries the same weight as showing two or more clues.1National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Participant Manual
What the Score Means
Two or more clues, or inability to complete the test, indicates a strong likelihood that your BAC is at or above 0.08. There’s no pass/fail — the officer records the number and type of clues, and that count becomes evidence. NHTSA research puts the accuracy of the two-clue threshold at 83% when officers are trained and follow protocol.1National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Participant Manual
The one-leg stand is rarely used alone. It sits alongside the Horizontal Gaze Nystagmus eye test and the Walk and Turn test, and officers typically run all three before deciding whether to request a breathalyzer or blood draw.3Office of Justice Programs. Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent One boundary worth knowing: the accuracy figures were validated for alcohol impairment. NHTSA has not published comparable accuracy percentages for drug detection through the one-leg stand, though certain patterns can suggest other substances.4National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Instructor Guide
Conditions the Officer Is Supposed to Check
Before the test starts, the officer should confirm the environment won’t unfairly affect your performance. The surface should be reasonably dry, hard, level, and non-slippery. If it isn’t, the NHTSA manual recommends moving the test to a better location or skipping the one-leg stand entirely and relying only on the eye test.1National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Participant Manual Lighting also has to be adequate for you to see the ground and for the officer to see your movements.
Footwear matters too. If you’re wearing heels higher than two inches, flip-flops, platform shoes, or anything else that would throw off your balance, the officer should offer you the chance to remove them before beginning.4National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Instructor Guide Skipping that step hands the defense a legitimate basis to question the result.
Who Has Trouble With This Test Even Sober
Standing on one foot for 30 seconds is genuinely hard for some people regardless of sobriety. The original SFST research identified groups who struggle with the one-leg stand for reasons that have nothing to do with alcohol:
- People over 65 had difficulty in the original studies.
- Individuals who are 50 or more pounds overweight showed similar difficulty, though NHTSA notes the original research didn’t actually record subjects’ weight in its final report.
- Back problems, leg injuries, and inner ear disorders all affect balance independently of impairment.1National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Participant Manual
Officers are supposed to ask about physical limitations before administering the test. If you have a condition that affects your balance, say so clearly and early. A documented medical issue that the officer ignored is one of the strongest challenges a defense attorney can raise. Even without a formal diagnosis, age and weight alone can support an argument that the result is unreliable.
Officer Errors That Weaken the Evidence
The 83% accuracy figure depends entirely on the officer following the protocol. Deviations are more common than you might expect, and each one creates an opening.
Timing mistakes are the simplest to prove. The test must last exactly 30 seconds. If the officer didn’t use a watch or other timing device, there’s no way to verify the duration was correct. An officer who cuts the test short or lets it run long has administered something other than the test NHTSA validated.
Instruction errors are equally damaging. The officer must demonstrate the stance and the counting method, ask whether you understand, and wait for your confirmation before giving the command to start.1National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Participant Manual Skipping any of those steps means the test wasn’t standardized.
Environmental failures are the third category. Administering the test on a sloped shoulder, a gravel lot, or under poor lighting violates the setup requirements. Not offering you the chance to remove unsuitable footwear is another procedural gap.4National Highway Traffic Safety Administration. DWI Detection and Standardized Field Sobriety Testing Instructor Guide Any of these issues can lead a court to reduce the weight of the test results or exclude them entirely.
Can You Refuse
Field sobriety tests are voluntary in most states. Unlike a breathalyzer or blood draw, which fall under implied consent laws, the one-leg stand is a roadside coordination exercise that you can usually decline without triggering an automatic license suspension. The U.S. Supreme Court drew the line in Schmerber v. California, holding that the Fifth Amendment protects you from being compelled to give testimonial evidence but does not cover physical evidence.5Library of Congress. Schmerber v. California, 384 U.S. 757 (1966) Your performance on the test can be used against you, but refusing to take it generally isn’t punishable by statute.
Refusing doesn’t make the situation go away. An officer who suspects impairment will likely move straight to requesting a chemical test, and refusing that carries real consequences under implied consent laws, typically a mandatory license suspension of several months to a year or more, and in some states the refusal itself can be introduced at trial. Declining the one-leg stand removes one piece of evidence but won’t stop the investigation.
How Results Are Used in Court
One-leg stand results feed into two separate proceedings in most jurisdictions: the criminal DUI case and an administrative hearing over your license. In both, the clue count gives prosecutors a quantifiable measure of impairment to present alongside chemical test results, dashcam footage, and the officer’s observations.
Defense attorneys challenge the test on the grounds above, and those challenges succeed more often when body camera footage contradicts the officer’s written report. If the video shows an uneven surface, a missing demonstration, or a count that ran well past 30 seconds, the test loses credibility quickly. Courts don’t treat field sobriety results as dispositive; they’re one data point among several. But a properly administered one-leg stand showing two or more clues, combined with consistent results on the other two SFST tests, gives prosecutors solid footing for a probable cause determination and often factors into the eventual outcome at trial.