DWI Arrests in Austin: How Traffic Stops, Field Sobriety Tests, and Breath Tests Are Challenged in Texas Courts

Did the officer have the legal right to keep investigating after the reason for the stop was over?

A Texas DWI investigation is usually a chain: the stop, the detention, the roadside testing, and then the breath test. If any link is weak, the State may be left arguing from assumptions instead of admissible proof.

After an arrest, call Austin DWI lawyers to preserve evidence and build challenges early. Next comes the question of what the officer relied on.

How Traffic Stops Are Challenged in Texas DWI Cases

Most DWI cases begin with a stop that the officer claims was based on a traffic violation or suspicious driving. In Texas, the defense often focuses on whether the officer had reasonable suspicion to stop the vehicle in the first place and whether the officer had a lawful basis to extend the stop into a DWI investigation. If the stop is not lawful, evidence gathered afterward can be suppressed under Texas exclusion principles, including Tex. Code Crim. Proc. art. 38.23.

A Texas DWI attorney will typically break the stop into a timeline: the initial driving observation, the moment emergency lights came on, the first interaction at the window, and the point when the officer escalated to DWI steps. Video matters because it often reveals whether the report matches reality.

Defense challenges commonly target:

Officers sometimes describe “weaving” or “failure to maintain lane” in vague terms. If the vehicle never crosses a lane marker, or if the deviation is minor and brief, the defense may argue the officer lacked an objective basis for a stop. A stop can also be challenged when the alleged violation is factually wrong or legally mistaken, such as misunderstanding an equipment rule or treating a lawful driving choice as suspicious without support.

Even when the initial stop is valid, the defense may challenge whether the officer unlawfully prolonged the encounter. Once the traffic mission is complete, continuing the detention requires a separate, articulable basis. Courts scrutinize whether “odor,” “bloodshot eyes,” or “nervousness” are being used as generic labels rather than meaningful, case-specific facts. Federal law also reinforces limits on stop extension.

How Field Sobriety Tests Are Challenged in Austin DWI Prosecutions

Field sobriety tests often feel decisive because they are performed in public, on camera, and under pressure. But the courtroom question is not whether the officer “felt convinced.” The question is whether the tests were administered and interpreted in a way a judge or jury should trust. The most common battery is the Standardized Field Sobriety Test (SFST) set developed and taught through NHTSA materials that require standardized procedures and scoring..

A TX DWI lawyer will often challenge SFSTs by showing that real roadside conditions and human factors undermine the claimed reliability. The defense also pressed whether the officer followed the required steps and whether the alleged “clues” are supported by video rather than conclusory narrative.

How HGN is challenged;

HGN is frequently presented as a scientific measure, but the defense focus is technical: stimulus distance, timing, head movement, lighting, and whether the officer properly checked for equal pupil size and tracking. If the officer rushes the test, changes distance, fails to maintain the correct pace, or does not document required observations, the result becomes less persuasive. The defense may also raise alternative explanations unrelated to alcohol and highlight that the officer’s training and accuracy matter because HGN is still administered and scored by a person, not a machine.

How Walk-and-Turn and One-Leg Stand are challenged:

These tests are divided-attention tasks that can be affected by stress, footwear, surface slope, weather, injuries, fatigue, and anxiety. In Austin, roadside conditions can vary widely, and video can show whether the surface was level, whether passing traffic created distraction, or whether lighting was poor. A Texas DWI lawyer will examine whether the officer gave complete instructions, performed a correct demonstration, and scored the test according to standard criteria rather than personal impressions.

Below is a quick framework for how SFST weaknesses are typically presented in court, because it tracks what jurors can understand and what video can confirm:

• Conditions: uneven pavement, rain, wind, lighting, passing vehicles, cramped shoulder space
• Instructions: incomplete or confusing directions, rushed explanation, no confirmation of understanding
• Demonstration: officer does not properly show the task, then penalizes the driver for errors
• Scoring: “clues” claimed in the report do not appear on video, or the officer inflates minor issues
• Alternative causes: injury, medical limitations, fatigue, nervousness consistent with performance

NHTSA recognizes that SFSTs depend on standardized administration, and validation research is not a guarantee for every field stop that deviates from protocol.

How Breath Tests Are Challenged in Texas DWI Litigation

A breath result is often treated like the final word. In reality, the defense can challenge the breath test on foundation, procedure, and interpretation. The courtroom issue is not simply “what number printed.” It is whether the State can prove the test was properly administered, the instrument was properly maintained, and the result should be trusted beyond reasonable doubt in the context of the whole case.

A Texas DWI attorney typically seeks the full packet: maintenance logs, reference checks, calibration records, operator certifications, and any notes about errors or irregularities. The defense also looks closely at how the test was conducted and documented, including whether the required observation period was followed.

Common breath-test challenges include:

Mouth alcohol and observation period disputes. Breath testing is intended to measure deep-lung air, not residual alcohol in the mouth from recent burping, regurgitation, dental issues, or recent consumption. If the observation period is incomplete or poorly documented, the defense may argue the number is less reliable.

Maintenance and quality control gaps. Instruments require regular checks and documentation. A missing record, an out-of-tolerance check, or unclear maintenance history can become a powerful cross-examination point. A TX DWI lawyer may argue that without clean, complete records, the State has not laid a proper foundation.

Interpretation issues. Breath testing relies on assumptions and is still a proxy measurement. Even when the number is admitted, the defense can argue the result should be weighed cautiously especially when the driving facts and SFST evidence are disputed.

Texas cases can also involve a refusal. Refusal can trigger administrative consequences and the State may attempt to use it as evidence at trial, but the admissibility and weight of that evidence depend on what warnings were given and how the encounter unfolded.

Courts also distinguish between breath and blood testing in constitutional analysis. The U.S. Supreme Court has addressed when breath tests may be taken incident to arrest and when blood tests generally require stronger justification, shaping how evidence is gathered and challenged.

Talk With a Texas DWI Attorney About Challenging the Stop and Tests

An Austin DWI case is not decided by suspicion alone. It is decided by what the State can prove, what evidence the court will allow, and whether the stop, field testing, and breath evidence hold up under scrutiny. Contact us today to request a comprehensive case evaluation with The Law Firm of Kyle K. Ringle, PLLC by calling 512-478-3056.