Understanding the NHTSA Standardized Field Sobriety Tests (FSTs)

If an officer suspects that you might be driving under the influence of alcohol, they will administer a series of physical tests called the Standardized Field Sobriety Tests or “SFST.”  Depending on how you perform these tests, the police officer may arrest you for DUI.  If you go to trial, the state prosecutor will play a video for the jury of the arresting officer conducting field sobriety testing. They may make arguments that your performance on the roadside test proves your impaired driving and ability to operate a motor vehicle safely. 

A jury may determine you’re guilty or innocent based on the Standard Field Sobriety Test performance and the breathalyzer test result.  If the Standardized Field Sobriety Testing was not administered by the law enforcement officer correctly, the DUI case might be thrown out by the court well before you ever get to the trial stage. That is why thoroughly examining the FSTs is critical.  

Understanding the NHTSA Standardized Field Sobriety Tests

The Standardized Field Sobriety Tests consist of three tests

The Horizontal Gaze Nystagmus Test, the Walk and Turn, and the One Leg Stand test.  Each test has a series of “clues” or “points” that the officer is looking for.  Points or clues in the Standardized Field Sobriety Tests are bad, as they are interpreted to indicate impairment.  Each test has a certain number of clues or points, which, if exceeding, an officer will conclude impairment.    

You are not legally obligated to perform the Standardized Field Sobriety Tests before you have been arrested.  

More information on each of the Field Sobriety Tests


The Horizontal Gaze Nystagmus test is a test that looks at your eyes as the officer passes a stimulus (finger or pen) in front of your eyes back and forth several times.

The test looks for involuntary jerking (“nystagmus”) of the eye that can be caused by a central nervous system depressant such as alcohol.  Because nystagmus is an involuntary reflex, you cannot control it and you cannot train yourself not to exhibit this trait.  However, other things can cause this jerking or nystagmus, and it is important to determine if any of those other factors are present (head trauma, flashing lights, other medication, medical conditions). 

The HGN test takes time to administer properly.  The officer must make several passes of the stimulus, look for indications of nystagmus at specific angles, and must not rush the test.  If the test is rushed, or the officer does not properly administer the test, the judge may suppress the test results so the state prosecutor cannot use them against you.  Proper cross-examination of the officer who conducted this test is critical to your DUI defense. 

Walk and Turn Test

The nine-step walk and turn test is a test that judges your ability to perform divided attention tasks, specifically, your ability to do physical tasks while simultaneously performing a mental task.  In this test, you must listen to the officer’s instructions while maintaining a certain standing position. 

When the officer instructs you to start, you must take nine heel-to-toe steps down an imaginary line while counting out loud.  At the end of the first nine steps, you must do a specific type of turn on your foot and then walk back down the imaginary line with nine additional heel-to-toe steps.  If you start early, step off the line, use your arms to balance, turn incorrectly, count incorrectly, or do not put your heel to your toe on each step, the officer will assign a “clue” or “point” which he will use to try to indicate impairment. 

This test can be difficult for people with any form of physical disability, injury, or in poor conditions (such as a snowy Park City road in January). It is important to evaluate whether other factors may have caused a person to exhibit these “clues” or “points” on the walk-and-turn test.  If enough of the “clues” or “points” can be discounted or your defense attorney can show the court that this test was administered incorrectly in violation of the National Highway Safety Traffic Administration Standards, it may be thrown out and not used against you in your DUI case.  

One Leg Stand

This test also asks a person to perform a physical activity while also performing a mental task (counting out loud).  A person is asked to choose a foot to lift off the ground approximately six inches, point the foot forward, and look at it while counting out loud for approximately 30 seconds.  The officer will evaluate if you hop, sway, put your foot down, count incorrectly or use your arms for balance. 

This test can be difficult for sober individuals, especially if they have any form of physical disability, injury, or are on that cold Park City, UT roadway in January.  The interpretation of this test, as with all the other FST tests, is subjective.  Your defense attorney needs to review the video of this test and determine if the arresting officer interpreted your performance in an overly harsh manner or assessed “points” or “clues” that really were not present.  If administered incorrectly, the test results may be suppressed by a court, and the results not used against you.  

Bangerter Law Firm has 16 years of experience evaluating standardized field sobriety tests. 

We have seen hundreds of police dashcam and bodycam videos. Bangerter Law can determine if the tests were administered according to the National Highway Traffic Safety Administration Standards and if other factors came into play that the officer missed, ignored, or even caused.  We will analyze your DUI case with an eye towards suppressing any evidence that was gathered illegally and will seek suppression of any such illegal evidence.  

Contact Bangerter Law Firm today for your free consultation. (305) 202-5332