Managing Attorney
In Houston and across Texas, one of the most critical components of a police officer’s DWI investigation involves the use of police balance tests. These tests, officially known as Standardized Field Sobriety Tests (SFSTs), are administered roadside to help officers determine whether a driver is intoxicated.
But how reliable are these tests? And more importantly, how can they be challenged in court? How can an experienced DWI attorney challenge SFSTs to show that a driver was not intoxicated and that the tests are unreliable or were not administered fairly?
Understanding Police Balance Tests
SFSTs are divided attention tasks designed to assess a driver’s balance, coordination, and cognitive function. The National Highway Traffic Safety Administration (NHTSA) recognizes three standardized tests:
- Horizontal Gaze Nystagmus (HGN) Test
- Walk-and-Turn (WAT) Test
- One-Leg Stand (OLS) Test
Each test is intended to identify signs of intoxication that allegedly correlate with a blood alcohol concentration (BAC) of 0.08 or more. In many Harris County DWI cases, these tests form the core of the evidence used to justify arrest.
The Legal Definition of Intoxication in Texas
Under Texas Penal Code §49.01(2), “intoxicated” means:
- (A) not having the normal use of mental or physical faculties by reason of the introduction of alcohol, a controlled substance, a drug, a dangerous drug, a combination of those substances, or any other substance into the body; or
- (B) having an alcohol concentration of 0.08 or more.
In Houston-area DWI arrests, police often rely heavily on SFST performance to justify an arrest and conviction under part (A) of the statute—especially when breath or blood test results are not available at the time of arrest.
Overview of Each SFST
1. Horizontal Gaze Nystagmus (HGN)
This test is frequently referred to as the “eye test.” This test checks for involuntary eye jerking as the eyes track a stimulus (typically a pen or flashlight). Officers look for six clues—three in each eye—including lack of smooth pursuit, distinct nystagmus at maximum deviation, and early onset of nystagmus before 45 degrees.
2. Walk-and-Turn (WAT)
The subject is instructed to take nine heel-to-toe steps in a straight line, pivot, and return the same way. Common “clues” include starting too soon, losing balance, stepping off the line, and taking the wrong number of steps.
3. One-Leg Stand (OLS)
The subject must raise one leg off the ground and count aloud for 30 seconds. Officers observe for swaying, hopping, putting the foot down, or using arms for balance.
These tests are regularly administered by Houston Police Department (HPD) officers, Harris County deputies, and local law enforcement across Southeast Texas.
Are Field Sobriety Tests Enough to Establish Probable Cause for a DWI Arrest in Texas?
In many Houston DWI arrests, police use SFST performance as the primary justification for placing a driver in custody. But field sobriety tests alone are not foolproof. If administered incorrectly—or if the driver’s poor performance can be explained by other factors such as injury, fatigue, or anxiety—they may not support a conclusion that the driver was intoxicated.
An experienced DWI defense attorney can challenge the officer’s conclusion that the tests provided proof of intoxication at trial, or the validity of the arrest through a motion to suppress, arguing that the officer lacked sufficient evidence. This is especially important in “no-test” DWI cases where there’s no breath or blood test to confirm intoxication.
How SFSTs Are Used in Court
In Harris County courtrooms, SFSTs are often presented to jurors as reliable indicators of intoxication. But these tests are subjective and prone to error. Officers may misinterpret signs, exaggerate performance issues, or conduct the tests under unfavorable conditions like poor lighting, rain, or uneven pavement.
Importantly, SFSTs must typically be administered according to strict NHTSA protocols under Texas law. If they are not, the tests can be challenged as invalid.
Challenging Field Sobriety Tests in Texas DWI Cases
A skilled DWI attorney can challenge the use of SFSTs in several ways:
1. Improper Administration
If the officer did not follow training procedures, such as failing to give proper instructions or demonstrating the test, the results can be called into question.
2. Medical Conditions or Physical Limitations
Issues like vertigo, prior surgeries, back injuries, diabetes, or neurological disorders can mimic signs of intoxication. Many Houstonians have health issues that police do not ask about before beginning these tests.
3. Environmental Factors
Was the roadside surface flat and dry? Was there heavy traffic or flashing lights? These conditions can affect a driver’s performance.
4. Fatigue or Anxiety
Late-night stops, bright lights, and nervousness can affect performance. Being tired or anxious is not the same as being intoxicated.
5. Cross-Examination of the Officer
A defense attorney can use cross-examination and video evidence to point out discrepancies in how the officer described the test versus how it was actually performed.
Suppression of the HGN Test in Texas DWI Cases
The Horizontal Gaze Nystagmus test is treated as scientific evidence in Texas courts. That means it must meet certain admissibility requirements under Texas Rule of Evidence 702.
Common Reasons for Challenging SFSTs:
- Improper administration: Officers must follow NHTSA’s 12-step procedure. Skipping steps or conducting the test improperly can lead to suppression.
- Lack of certification: Officers must be trained and certified to administer the HGN test. If not, the evidence may be excluded.
- Medical or visual issues: Eye problems, medications, or neurological conditions can cause nystagmus unrelated to alcohol.
- Poor conditions: External distractions like headlights, traffic, or loud noises can affect both the test and its interpretation.
If a judge rules the HGN inadmissible, it can severely weaken the prosecution’s case—especially when there is no BAC result.
Frequently Asked Questions (FAQ)
Can you refuse a field sobriety test in Texas?
Yes. These tests are voluntary in Texas. You can decline without automatic penalties, although officers may still arrest you.
What happens if I fail a balance test but pass a breath test?
You can still be charged under the “loss of mental or physical faculties” clause, which does not depend on a specific breath or blood result. However, your attorney can argue the breath test disproves intoxication.
Can medical conditions affect the HGN test?
Absolutely. Inner ear disorders, eye muscle conditions, and neurological issues can cause false positives.
Is SFST evidence valid if there’s no video?
Yes, but it’s less persuasive. Defense attorneys can highlight the lack of footage and use it to challenge the officer’s credibility.
Are SFSTs reliable in Houston traffic stop conditions?
Not always. Many Houston DWI arrests occur on busy freeways, dark side streets, or in poor weather—all of which can affect SFST results.
Defending DWI Cases Based on Field Sobriety Tests in Houston and Beyond
Standardized Field Sobriety Tests are widely used by law enforcement in Houston and surrounding areas—including Harris County, Montgomery County, Fort Bend County, and Galveston County—but they are far from infallible. Their reliability depends on strict adherence to testing protocol and an officer’s fair interpretation. Unfortunately, both are frequently lacking.
At Ceja Law Firm, we focus on identifying these weaknesses. Attorney Jose Ceja has completed hundreds of hours of advanced training in breath, blood, and field sobriety testing and is certified to administer the same SFSTs used by police. That means we don’t just challenge the tests—we know how they’re supposed to work.
If you’ve been arrested for DWI in Houston or the surrounding areas based on balance tests or the HGN test alone, don’t assume the case is open and shut. Contact Ceja Law Firm today to schedule a personalized consultation and begin building your defense. Ceja Law Firm represents clients charged with DWI throughout Harris County, including Houston, La Porte, Pasadena and Baytown.
