Field Sobriety Tests (SFST)
Before any machine got involved, an officer probably asked you to step out of your car and perform “field sobriety tests” on the side of the road. These roadside exercises feel like a fair chance to prove your sobriety. They aren’t. They’re designed to be failed, scored subjectively by the same officer who already decided to pull you over, and in Texas, you were never required to do them at all.
The three “standardized” tests
The National Highway Traffic Safety Administration (NHTSA) recognizes exactly three Standardized Field Sobriety Tests (SFSTs):
- Horizontal Gaze Nystagmus (HGN): following a pen or light with your eyes while the officer looks for involuntary jerking.
- Walk-and-Turn (WAT): taking nine heel-to-toe steps, turning, and returning.
- One-Leg Stand (OLS): standing on one foot while counting.
Even NHTSA’s own validation research says these are only partly accurate: roughly 88% for HGN, 79% for Walk-and-Turn, and 83% for One-Leg-Stand: and only when administered exactly according to protocol. In the real world, on a sloped Houston shoulder, in the dark, in traffic, with a nervous driver in the wrong shoes, that protocol is rarely followed to the letter.
Watch: The Field Sobriety Tests, Explained
Short breakdowns of each standardized test, what the officer is scoring, and whether you have to perform them at all.
What are standardized field sobriety tests?
The horizontal gaze nystagmus (eye) test
The walk and turn test
Can you refuse field sobriety tests?
Why field sobriety tests are so easy to challenge
- They’re subjective. The officer decides what counts as a “clue.” Two officers can score the same performance differently.
- Innocent explanations abound. Age, weight, injuries, inner-ear and balance disorders, neurological conditions, fatigue, footwear, uneven pavement, weather, and simple nerves all produce “clues” that have nothing to do with alcohol.
- HGN is medical testimony from a non-doctor. Nystagmus has dozens of natural causes; an officer is not a physician and often can’t distinguish alcohol-related nystagmus from the many benign kinds.
- Non-standardized “tests” have no validation. Reciting the alphabet, counting backward, or the finger-to-nose test are not scientifically validated at all, yet officers still use them.
- Improper instructions and demonstrations. If the officer gave confusing instructions or demonstrated the test incorrectly, your “failure” is meaningless.
You can refuse field sobriety tests in Texas
Unlike a breath or blood test, refusing field sobriety tests carries no automatic license penalty in Texas. They are voluntary. (The officer may still arrest you based on other observations, and refusal doesn’t end the case, but it removes one set of subjective evidence.) If you already took them, that’s not the end of the story: how they were administered and scored is exactly what we attack.
Did the roadside tests decide your case? Call Blass Law at (713) 664-4000. We review the dashcam and bodycam footage frame by frame, measure the officer’s instructions against NHTSA standards, and surface every innocent explanation the officer ignored.
(Related: breath test defense · blood test defense · first-offense DWI · DWI cost)
Related: How we challenge DWI tests · Breath test defense (Intoxilyzer 9000) · Blood test defense & lab errors
Reviewed by Jay Blass Cohen, founder of Blass Law PLLC, ACS-CHAL Forensic Lawyer-Scientist, certified Drug Recognition Expert, and SFST instructor, serving Houston since 2009. This article is general information, not legal advice for your situation. Prior results do not guarantee a similar outcome.