Lawyer For Standardized Field Sobriety Tests (SFSTs) In Fort Bend County

Fort Bend Standardized Field Sobriety Tests

The Standardized Field Sobriety Test (SFST) battery is composed of three tests: Horizontal Gaze Nystagmus (HGN), Walk-and-Turn (WAT), and One-Leg Stand (OLS).  The tests were developed by the National Highway Traffic Safety Administration (NHTSA) in the late 1970’s. In 1981, law enforcement officers began using the NHTSA sobriety tests at a roadside to help determine whether motorists who are suspected of DWI have blood alcohol concentrations (BACs) greater than 0.10 percent. Since 1981, however, many states including Texas have implemented laws that define DWI at BACs below 0.10.

The validity of SFST results is dependent upon officers following the established, standardized procedures for test administration and scoring.  According to NHTSA when properly administered, scored and under laboratory conditions, the accuracy of the SFSTs in correctly identifying intoxicated drivers is as follows:

  • Horizontal Gaze Nystagmus (HGN) – 77%
  • Walk and Turn (WAT) – 68%
  • One Leg Stand (OLS) – 65%

This means that even under laboratory conditions, the HGN was wrong 23% of the time, the WAT 32% and the OLS 35% of the time.  Additionally, NHTSA’s own research emphasizes that test results are valid only when administered in strict compliance with NHTSA protocol.  If anyone of the standardized field sobriety elements is changed, the validity is compromised.  It is, therefore, imperative to have a qualified DWI attorney review the manner in which the SFSTs were administered to determine whether the results may be suppressed.

Horizontal Gaze Nystagmus

“Nystagmus” means an involuntary jerking of the eyes.  HGN refers to an involuntary jerking occurring as the eyes gaze toward the side.  In addition to being involuntary, the person experiencing the nystagmus is unaware that the jerking is happening.  The theory behind the test is that nystagmus becomes readily noticeable when a person has a blood alcohol concentration of .08 or above.

In administering the test the officer has the subject follow the motion of a stimulus with the eyes only.  The stimulus may be the tip of a pen, penlight,  eraser on a pencil or a fingertip.  As the eyes move from side to side each eye is examined for three specific clues:

  • Lack of Smooth Pursuit – does the eye move smoothly or does it jerk in a side to side manner
  • Distinct and Sustained Nystagmus at Maximum Deviation – when the eye moves as far to the side as possible and is kept at that position for at least four seconds, does it jerk side to side in a distinctive manner
  • The onset of Nystagmus Prior to 45% – as the eye moves to the side, does it start to jerk prior to reaching a 45% angle? 

Police frequently fail to properly administer the HGN.  It is crucially important for an experienced DWI attorney to review the videotape, if available to ascertain whether the test was properly administered or whether suppression of the results is possible.

Walk and Turn

The walk and turn is a divided attention test consisting of two stages: Instruction Stage and Walking Stage.  In the instruction stage, the subject must stand with his feet in a heel-to-toe position, keep his arms at his sides, and listen to instructions.  The subject must maintain the heel-to-toe position and may not begin walking until all instructions are given.  In the Walking Stage, the subject takes nine heel-to-toe steps, turns in a prescribed manner, and takes nine heel-to-toe steps back while counting out loud and watching his feet.  Officers observe the subject’s performance for eight clues:

Instruction Stage:

  • can’t maintain balance
  • starts too soon

Walking Stage:

  • misses heel to toe
  • steps off the line
  • wrong number of steps
  • uses arms for balance
  • stops while walking
  • improper turn

A person who exhibits two or more clues is classified as intoxicated

One Leg Stand

The one leg stand is also divided into two stages.  In the Instruction Stage, the subject must stand with feet together, keep arms at side and listen to instructions.  In the Balance and Counting Stage, the subject must raise the leg of his choice approximately 6 inches off the ground, toes pointed out, keeping legs straight.  While looking at the elevated foot, count out load in the following manner: “one thousand and one, one thousand and two”, etc, until told to stop.  The officer will instruct the subject to stop after 30 seconds.  The subject is observed for the following clues:

  • puts a foot down
  • sways
  • uses arms for balance
  • hops

A person who displays two or more clues will be classified as intoxicated.

What Does All this Mean to your Case?

As a practical matter, it is not important for a person to perform perfectly on the field sobriety tests.  What is important is that your performance on these tests was normal.  Normal for YOU, given all the circumstances.  Did the officer give the proper instructions and demonstration?  Was the test scored properly?  Were there any factors that interfered with your ability to perform at your best?  To answer these questions we will need to review the video, police reports as well as your recollection.  Is there anything in your medical history that is relevant?  For example, NHTSA has determined that people with leg, back and knee problems will have trouble doing these tests, as will those over age 65 and persons more than 50 pounds overweight.

I ask the jury to take a common sense approach to evaluating a client’s performance on sobriety tests.  After all most people have never attempted these tests before.  The police do not give a person the chance to practice nor do they give the nervous driver a second chance.  Many officers will even admit that they have seen fellow officers perform poorly on these tests when completely sober.