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Standardized Field Sobriety Tests: What Are They?

Posted by Erik Fine | Apr 10, 2020 | 0 Comments


     The purpose of this blog is to give the reader a general understanding of what Standardized Field Sobriety Tests (SFST) are and how law enforcement uses them in deciding if you are going to be arrested for Driving under the Influence (DUI).  It would be impossible to explain all of the intricate details involved in administering and interpreting the results of SFSTs in a blog post, but this blog will certainly help remove the mystery of what SFSTs are and how law enforcement officers use them to determine if you are too impaired to safely operate a vehicle.  Any specific testing procedures that are cited in this blog come from the DWI Detection and Standardized Field Sobriety Testing Participant Manual  Revised Edition 02/2018. 

     Before I became an attorney, I was a police officer.  Not just a police officer, but a traffic division police officer.  I received very specialized police training on DUI detection and enforcement, well above what average police officers receive in the police academy or even while working the streets.  Before I was made the supervisor of the Traffic Division, I spent most of my police career on the midnight shift where I had the opportunity to polish my DUI detection and enforcement skills.  When I tell you that I really knew how to do my job, what I'm really trying to say is that I was as close to being an expert at DUI detection and enforcement as a police officer could boast.  I knew (and still know) all of the tricks of the trade.  I've made countless DUI stops and DUI arrests during my law enforcement career.  In all my years in law enforcement, I don't think I ever lost a DUI case because I made ROCK SOLID DUI CASES!  As a criminal defense lawyer, I am able to put almost two decades of law enforcement experience to work for my clients.

     When an officer makes a traffic stop and then decides that he may have a DUI suspect and needs to administer SFSTs to the driver, there are three (3) SFSTs that he will give to the driver:

  1.    Horizontal Gaze Nystagmus  (an eye test)
  2.    Walk-and-Turn
  3.    One Leg Stand      

     Sure, there are other tests that police officers may use to assist an officer in determining if a driver is intoxicated, but the three SFSTs I just mentioned were developed by The National Highway Traffic Safety Administration (NHTSA) and the U.S. Department of Transportation (U.S. DOT) to be the ONLY testable, reliable and determinate field sobriety tests that law enforcement officers should do in the field to determine if a driver is impaired to the point of being an unsafe driver.  There is a separate battery of field sobriety tests that are used when a marine police officer is testing a boat operator for Boating Under the Influence  (and yes, I've successfully represented clients who were charged with BUI).  These three tests are taught to police recruits in police academies across the United States by certified SFST instructors.  That is why they are called "standardized."  Standardized Field Sobriety Testing instruction given to police officers includes classroom lectures, written officer testing on the classroom lectures, and practical "hands on" examination of intoxicated volunteers under controlled conditions in the police academy.  A police officer cannot graduate the police academy without successfully passing all aspects of their SFST training.  This training is not easy, I assure you.

     My experience as a police officer, a field training officer (FTO), a traffic division supervisor, a patrol division commander and certified accident reconstructionist is that police officers RARELY administer the SFSTs exactly and subjectively as their training mandates.  In the NHTSA Standardized Field Sobriety Test manual, officers are instructed and taught that if the SFSTs are not given exactly and correctly that the test results are NOT to be considered tainted and therefore invalid in court.  I've personally administered literally hundreds of SFSTs to drivers and watched other officers give just as many.  I'm here telling you right now that those tests are improperly administered to suspected impaired drivers at least 80% of the time.  It is extremely difficult for police officers to administer a battery of SFSTs perfectly and exactly all of the time.  After all, they are only human.  

     The rationale behind the three SFST designed and developed by NHTSA and USDOT and written into the DWI Detection and Standardized Field Sobriety Testing Participant Manual is that it is asserted that SFSTs test for what is known as Typical Simultaneous Capabilities Required for Driving.  That is, "any test that requires a driver to demonstrate at least two or more of these capabilities  simultaneously is potentially a good psychophysical test" (DWl Detection and Standardized Field Sobriety Testing Phase Three:  Pre-Arrest Screening, Session 7, page 14).   Additionally, the manual theorizes that field sobriety tests should be reasonably simple for the average person to complete as instructed when sober ( 15).  According to the cited SFST participant manual, those driver capabilities are:

  •    Information processing
  •    Short-term memory
  •    Judgment / decision making
  •    Balance
  •    Steady, sure reactions
  •    Clear vision
  •    Small muscle control
  •    Coordination of limbs  


     In Alabama, Horizontal Gaze Nystagmus is NOT  currently a legally acceptable field sobriety test because there has yet to be established case law "precedent" under what lawyers know as the Daubert Standard.  However, the test is still taught to police recruits in the academy and administered to drivers on the roadway.  The results from the HGN test then become part of a mosaic of evidence or pieces of a puzzle in assisting an officer in determining if he should affect a DUI arrest, but those results will be inadmissible in court.

     HGN is the name given to the involuntary jerking of the eyes that occurs as the test subject's eyes gaze from side to side.  Nystagmus is caused by alcohol and / or other drugs and some medical conditions (DWI Detection and Standardized Filed Sobriety Testing Participant Manual, Review and Proficiency Examinations, Session 15, page 4).  The police officer holds a pen  in front of a driver's eyes and has him track the pen as the officer moves the pen form side to side without the test subject being allowed to move his head, just track the pen his eyes.  The officer is looking for three (3) clues in each eye:  Lack of Smooth Pursuit, Distinct and Sustained Nystagmus at Maximum Deviation, and Onset of Nystagmus Prior to 45 Degrees (Id. at 5).

     There are more procedural requirements necessary to properly administer the HGN test to drivers, but since the results of HGN are NOT admissible in court, I have chosen not to spend much time discussing the test.


     The Walk-and-Turn (WAT) is a divided attention test comprised of a mental task as well as a physical task.  This test is a two stage test that encompasses both an instructional stage and a walking stage.  The driver is instructed to place his right foot on "the line" ahead of his left foot, standing in a heel-to-toe fashion while keeping his arms at his sides.  The driver is then instructed NOT to begin the test until instructed to do so by the officer.  The driver is then instructed to take nine (9) heel-to-toe steps without falling off "the line" or using his arms for balance.  Once he has completed the nine (9) steps, the driver is to take a small series of steps to turn back around and walk nine (9) heel-to-toe steps in the same manner.  Additionally, the test subject is instructed to keep watching his feet with his arms at his sides, counting the steps out loud and not to stop walking once he begins. 

     There are eight (8) possible clues of impairment that the officer watches for during the WAT: (Id. at 15,16)

  1.    Subject cannot keep balance (feet break away from the heel-to-toe stance)
  2.    Subject starts too soon (subject starts to walk before being told to do so)
  3.    Subject stops while walking
  4.    Does not touch heel-to-toe
  5.    Subject steps off "the line"
  6.    Uses arms for balance
  7.    Improper Turn
  8.    Incorrect number of steps      

     According to the cited participant testing manual, if a driver displays two (2) or more clues of impairment, the Walk-and-Turn test is 79% accurate in determining that the test subject has a Blood Alcohol Concentration (BAC) above 0.08 (Id. at 17).


     The One Legged Stand is also a divided attention test (a mental and a physical task) that comprises a two stage test, an instructional stage and a balance and counting stage (Id. at 18).  The test subject is told to stand with his feet together and arms resting at his sides and to hold that position until he is told to begin the test.  The test subject is then instructed by the police officer to raise either one of his legs six inches off of the ground, keeping his raised leg parallel to the ground and straight.  He is told to keep both arms at his side and to look directly at the elevated foot and to count out loud, "one thousand one, one thousand two, one thousand three, until told to stop counting.

     There are four (4) specific clues of impairment for the OLS test: (Id at 21,22) 

  1.    Sways while balancing
  2.    Uses arms for balance
  3.    Hopping
  4.    Puts foot down

   According to the cited participant manual, if a driver displays two (2) or more clues of impairment, the One Legged Stand is 83% accurate in determining that the test subject has a Blood Alcohol Concentration (BAC) above 0.08 (Id. at 22) .

     There is so much involved in administering SFSTs and interpreting those results.  All of this happens on the side of the road in less than ideal testing circumstances.  This is just a thumbnail sketch of the SFST procedures.  Obviously, there is a tremendous amount of subjectivity involved with determining if a driver is too intoxicated to safely operate a vehicle.  I would like to close this blog out with three pieces of advice:

  1.    NEVER drink and drive
  2.    NEVER take field sobriety tests UNLESS you haven't had any alcohol or controlled substances (you may politely refuse to be tested)
  3.    ALWAYS hire a lawyer who used to be a police officer and knows ALL of the tactics and techniques used inside and out  

     Not participating in the SFSTs could (and probably will) force the officer to take you to jail for DUI. There may be other factors that convince the officer that you are too impaired to operate a vehicle safely.  What I am suggesting is that you may be better off in the trial phase of your DUI case to not have given the officer poor SFST results that would be bad for you if presented in court.  Don't forget, most law enforcement agencies have body cameras that record everything that is said and done during the traffic stop.   


About the Author

Erik Fine

Attorney Erik D. Fine, A.A., B.S., J.D. Mr. Fine, an Alabama native, is a graduate of Mountain Brook Public Schools. He received an athletic scholarship to play baseball at Kansas City Kansas Community College from which he graduated with an Associates Degree in Law Enforcement in 1989. It was i...


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