An officer asks you to step out of the car and follow a pen with your eyes. Then walk a line heel to toe. Then stand on one leg and count. Nobody tells you these are optional, and almost nobody asks. Understanding what a field sobriety test in Texas is designed to measure, and how far short of that design it usually falls, changes how you see everything that happened on that roadside.
The three standardized tests were never built to prove intoxication. They were built to help an officer decide whether to arrest. That distinction gets lost between the shoulder of the highway and the courtroom, and it is one of the more productive places for a defense attorney to work. Our DWI attorneys in Conroe examine this evidence in every case, and this article explains what we look for.
Are Field Sobriety Tests Required in Texas?
No. Field sobriety tests are voluntary in Texas. There is no statute compelling you to perform them and no license consequence for declining, which distinguishes them sharply from breath and blood testing under the implied consent rule in Transportation Code Section 724.011.
Officers are not required to tell you the tests are optional, and they rarely do. The request is usually phrased as an instruction. Politely declining is lawful, though it will not prevent an arrest if the officer already believes there is probable cause. What it does prevent is the creation of a video record showing you struggling with a test that most sober people also fail under roadside conditions.
The Three Standardized Tests and What Each Measures
The National Highway Traffic Safety Administration validated three tests in the 1970s and 1980s. Texas officers are trained on this battery, and departures from the training manual are a legitimate basis for challenge.
Horizontal Gaze Nystagmus
Nystagmus is an involuntary jerking of the eye. The officer moves a stimulus horizontally and watches for lack of smooth pursuit, distinct jerking at maximum deviation, and onset of jerking before 45 degrees. Six total clues are possible, three per eye, and four or more is scored as a failure.
The problem is that nystagmus has dozens of causes unrelated to alcohol. Inner ear conditions, head injury, certain prescription medications, fatigue, caffeine, influenza, and simple natural variation all produce it. Officers are not trained to distinguish among these causes, and they are certainly not qualified to render a medical opinion about them.
Roadside conditions make it worse. Passing headlights, flashing emergency lights, and wind all interfere with the eye’s ability to track smoothly. When we review dash camera footage and see the officer conducting an HGN test with strobing overheads directly behind the driver, that result becomes very difficult for the State to defend.
Walk and Turn
This is a divided attention test. You listen to instructions while holding a heel-to-toe stance, then take nine steps out, turn in a prescribed manner, and take nine steps back. Eight clues are scored, and two are enough to fail.
The clues include starting too soon, stopping while walking, stepping off the line, using arms for balance, and taking the wrong number of steps. Notice that several of those describe ordinary human behavior on uneven pavement in the dark.
NHTSA’s own materials note that the test requires a dry, hard, level, nonslippery surface with adequate lighting. Highway shoulders on Interstate 45 rarely qualify. Neither do gravel lots off Highway 105 or the sloped ramps around Lake Conroe.
One Leg Stand
You raise one foot roughly six inches, look at your toe, and count aloud for thirty seconds. Four clues are scored: swaying, using arms for balance, hopping, and putting the foot down. Two clues is a failure.
Age, weight, footwear, and orthopedic history all affect performance dramatically. NHTSA has acknowledged that individuals over 65, people more than 50 pounds overweight, and those with back, leg, or inner ear problems may have difficulty regardless of sobriety.
How Accurate Are These Tests, Really?
The validation studies reported accuracy rates in the range of 77 percent for HGN, 68 percent for walk and turn, and 65 percent for one leg stand at detecting a blood alcohol concentration above the legal threshold. Those figures come from controlled research conditions, not from a roadside at 1 a.m. with traffic passing at 70 miles per hour.
Read those numbers the other way. Under laboratory conditions, roughly one in three people who fail the one leg stand were not above the limit. That is not a scientific instrument. It is a screening tool with a meaningful error rate, presented to juries as though it were a measurement.
Non-Standardized Tests Carry Even Less Weight
Officers sometimes add tests that were never validated at all: reciting the alphabet without singing, counting backward, touching finger to nose, or the Romberg balance test. None of these has an established correlation with blood alcohol concentration. Texas courts have permitted testimony about them, but their evidentiary value is weak and cross-examination on the absence of any validation study is straightforward.
What We Look For When Reviewing the Video
In our experience defending DWI cases in Montgomery and Walker Counties, these are the recurring problems.
- Instructions given incorrectly or incompletely. The manual specifies exact wording and a demonstration. Officers frequently rush both, then score the driver for failing to follow instructions that were never properly given.
- Scoring clues that are not visible on video. An officer’s report lists six HGN clues. The camera cannot see eyes at that distance. The report becomes unverifiable, and the jury has to take it on faith.
- Unsuitable surface or lighting. Sloped shoulders, loose gravel, standing water, and strobing lights all appear in the footage and all violate the testing conditions the officer was trained to require.
- Ignoring disclosed medical conditions. When a driver mentions a knee replacement or vertigo and the officer proceeds anyway without adjusting, that is documented on the recording.
- Footwear. Officers are supposed to offer the opportunity to remove high heels. Many do not.
- The driving itself. If the initial stop was for an expired registration and the driving was otherwise unremarkable, the case rests almost entirely on the roadside tests.
What Happens After the Tests
Poor performance on field sobriety tests supplies probable cause to arrest. From there the case moves to chemical testing, and in Montgomery County that frequently means a blood draw under a warrant. Our page on breath and blood testing in Texas DWI cases covers what happens next, and the broader sequence is laid out in our overview of the Texas DWI legal process.
If no chemical test was obtained, the field sobriety results become the centerpiece of the State’s case. That is precisely when a thorough review of the video matters most, because there is nothing else holding the prosecution together.
Local Context in Montgomery and Walker Counties
Roadside conditions here are genuinely bad for testing. The Interstate 45 corridor through Conroe and The Woodlands has narrow shoulders with pronounced camber and constant high-speed traffic passing within feet of where drivers are asked to balance. Highway 105 toward Montgomery and the FM roads around Lake Conroe often have no shoulder at all, so tests get administered in parking lots or on gravel.
Walker County stops along Interstate 45 north of Huntsville present the same issues, compounded by limited lighting outside the city.
Montgomery County juries are not naive about this. Many of them drive those same roads. When a defense attorney can show the actual surface where a client was asked to walk a straight line heel to toe, the test result carries a good deal less weight than the offense report suggests.
Frequently Asked Questions
Can I refuse a field sobriety test in Texas without penalty?
Yes. Field sobriety tests are voluntary and carry no automatic license suspension for refusal. That is different from refusing a breath or blood specimen after arrest, which does trigger an administrative suspension.
Will refusing make me look guilty?
A prosecutor may comment on it, but declining a voluntary test is not evidence of guilt in the way a chemical test refusal is. Many attorneys consider declining the safer choice given the tests’ error rates.
What if I have a medical condition that affects balance?
Tell the officer at the time and make sure it is on the recording. Then gather medical records. Documented orthopedic, neurological, or inner ear conditions are among the strongest challenges to walk and turn and one leg stand results.
Does failing field sobriety tests mean I will be convicted?
No. The tests establish probable cause to arrest, which is a far lower standard than proof beyond a reasonable doubt. Many cases with poor roadside performance resolve favorably once the video and the officer’s methodology are examined.
Can the HGN test be used at trial in Texas?
Yes, but with limits. Texas courts allow an officer to testify that HGN indicates intoxication, but not to correlate the result to a specific blood alcohol number. Officers sometimes cross that line, and it is objectionable when they do.
What if the officer did not record the tests?
The absence of video is itself an issue worth raising. Without a recording, the jury has only the officer’s recollection, and that recollection was written after an arrest decision had already been made.
Your Next Step
A failed roadside test is an opinion formed in ninety seconds under poor conditions by someone who had already decided to investigate you. It is not a measurement, and it is not the end of your case.
Griffin & Cain, Attorneys at Law reviews the full video record, the officer’s training materials, and the testing conditions in every DWI case we take in Montgomery and Walker Counties. Schedule your consultation with criminal defense attorney Stella A. Stevens to have your roadside evidence examined. Contact our Conroe office today. We serve Conroe, The Woodlands, Montgomery, Magnolia, Willis, and Huntsville.
