Field Sobriety Tests in Texas: How We Challenge Them in Montgomery County

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Field Sobriety Tests in Texas: How We Challenge Them in Montgomery County

These tests are not as scientific as police want you to believe — and small mistakes can destroy their credibility.

What Are Field Sobriety Tests?

When an officer suspects a driver of being intoxicated in Texas, they will often use a set of roadside exercises developed by the National Highway Traffic Safety Administration (NHTSA) to determine whether to arrest. These are known as Standardized Field Sobriety Tests (SFSTs), and the three commonly administered are:

• Horizontal Gaze Nystagmus (HGN)
• Walk-and-Turn (WAT)
• One-Leg Stand (OLS)

Their purpose is not to measure driving ability, but rather to help the officer build “probable cause” for arrest. The problem? Human judgment plays a massive role — and human judgment is flawed.

How Officers Are Supposed to Administer SFSTs

NHTSA requires officers to follow specific instructions and evaluation guidelines. For example:

• HGN must be conducted with a proper stimulus at a set distance from the eyes
• WAT must occur on a dry, level surface with adequate lighting
• OLS requires a stable surface and shoes appropriate for balance

Any deviation — even a small one — reduces the scientific validity of the result. Unfortunately, real-world DWI stops rarely happen in perfect conditions.

Common Problems We Uncover in Montgomery County Cases

Video review often reveals:

• Improper instructions that confuse the driver
• Gravel, slopes, debris, or rain impacting balance
• Heavy traffic distracting or frightening the person
• Medical issues (vertigo, knee/hip problems) ignored by the officer
• Fatigue or anxiety mistaken for impairment

Many drivers are terrified — and nervousness doesn’t equal intoxication.

The Science Is Not Perfect

NHTSA studies show these tests have error rates even when done correctly:

Test	Accuracy Rate
HGN	77%
Walk-and-Turn	68%
One-Leg Stand	65%

Imagine if a doctor used a test that was wrong one-third of the time. Would you call that reliable?

HGN: The “Star Witness” We Attack First

Officers love to use HGN as “scientific” evidence. We routinely expose weaknesses such as:

• Not checking for equal pupil size or resting nystagmus
• Moving the stimulus too fast
• Holding it too high or too low
• Ignoring eye injuries or neurological issues

When the HGN falls apart, the entire probable cause argument suffers.

Balance Tests Can Be Unfair

Walk-and-Turn and One-Leg Stand heavily rely on balance and coordination — both of which may decline due to:

• Age
• Obesity
• Fatigue
• Injury
• Poor footwear

You may be perfectly sober yet still fail in the dark on the side of FM 1488 at midnight with trucks rushing past.

The Bodycam Changes Everything

In Montgomery County, the most powerful defense tool is usually the police body-worn camera. If the officer misjudged or exaggerated performance — the video often proves it.

We demand and review every second of:

• Dashcam
• Bodycam
• Station footage
• Phlebotomy room or breath test room video

Jurors appreciate accuracy. They don’t like guesses.

How We Use SFST Errors to Win

Our defense strategy includes:

• Pretrial suppression motions
• Cross-examining officer training and certification
• Contradicting the written report with video evidence
• Highlighting physical/medical factors unrelated to alcohol

If the foundation of probable cause collapses — so does the arrest and everything that followed.

Protect Your Rights Today

If you were asked to perform roadside tests in Montgomery County, the next steps matter. Don’t assume you “failed.”

Call now: (936) 777-4891

Disclaimer: Informational only — not legal advice. Talk directly with a Texas DWI defense attorney about your specific case.

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