Anthony R. Segura



Two Sugar Creekl Center Blvd

77 Sugar Creek Center Blvd, Ste 565

Sugar Land, Fort Bend County, Texas 77478

Practice Areas
Contact Us

15 days to save your license



Field Sobriety Testing

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 NHTSA's Standardized Field Sobriety Test (SFST) battery at 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 and scored, under laboratory conditions, the accuracy of the SFSTs in correctly identifying intoxicated drivers is as follows

  • HGN - 77%

  • WAT - 68%

  • 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 contact a skilled Sugar Land DWI Lawyer to review the manner in which the SFSTs were administered.  An experienced DWI lawyer may be able to suppress the results of an improperly administered test.

Sober People Fail Field Sobriety Tests Too

It is not uncommon for a completely sober person to fail a field sobriety test.  The tests are designed to place a person in an unnatural and uncomfortable posture.  The police do not explain how the tests are graded nor is the subject offered an opportunity to practice or a second chance.  The NHTSA training manual acknowledges that individuals with back, leg, knee problems and those over the age of 65 and persons more than 50 pounds overweight are likely to have difficulty performing the tests.

Horizontal Gaze Nystagmus (HGN)  

"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 is impaired.

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 or penlight, an 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 slowly or does it jerk noticeably?

  • Distinct Nystagmus at Maximum Deviation - when the eye moves as far to the side as possible and is kept at that position for several seconds, does it jerk distinctly?

  • Onset of Nystagmus Prior to 45% - as the eye moves to the side, does it start to jerk prior to a 45% angle?

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

Walk & Turn (WAT)

The WAT is a divided attention test consisting of two stages: Instruction Stage; and Walking Stage.  In the instruction stage, the subject must stand with their feet in heel-to-toe position, keep their arms at their 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 their feet.  Officers observe the subject's performance for eight clues:

  • can't balance during instructions

  • starts too soon

  • stops while walking

  • misses heel to toe

  • steps off line

  • uses arms for balance

  • improper turn; and

  • wrong number of steps

A subject who exhibits two or more clues fails the test.  Scoring is entirely subjective and within the officer's discretion.  

One Leg Stand (OLS)

The OLS 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:  

  • sways while balancing

  • uses arms to balance

  • hops

  • puts foot down

A subject who exhibits 2 or more clues will fail the test.

Free Consultation - Call Now

Sugar Land DWI Lawyer Anthony R. Segura has successfully completed the National Highway Traffic Safety Administration DWI Field Sobriety Training Course.  This is the same training that police receive.  Mr. Segura has extensive experience defending person charged with intoxicated offenses in Sugar Land and Fort Bend County. Contact him at 281-240-DWI-1 to learn how he can help you.

Anthony R. Segura | 77 Sugar Creek Center Blvd, Suite 565 | Sugar Land, Fort Bend County, Texas 77478
Phone: 281-240-3941
Copyright 2005. Broussard, McLaughlin & Segura. All rights reserved.