The legal definition of driving while intoxicated in Texas is not limited to a blood or breath alcohol concentration of .08% or higher. Under Texas Penal Code Section 49.01(2), a person is intoxicated if they have lost the normal use of their mental or physical faculties due to the introduction of alcohol, a controlled substance, a drug, or any combination of those substances. Texas law allows a DWI case to be based on either the theory of per se BAC intoxication or evidence that alcohol or drugs impaired a driver’s normal mental or physical faculties.

An officer can still arrest you if they establish probable cause for impairment based on the totality of facts, even without a breathalyzer reading above .08%. If your driving behavior, your appearance, your speech, or your performance on field sobriety tests suggests impairment, you can be arrested regardless of your BAC reading.

How Officers Determine Impairment Without Relying on BAC

Officers are trained to detect signs of impairment through observation, questioning, and standardized field sobriety tests.

When a Bryan officer pulls someone over on Highway 21 or near Texas Avenue, they are watching from the moment the stop begins. Slurred speech, bloodshot eyes, slow reactions, the smell of alcohol, or unsteady movement can all factor into an officer’s determination that your normal faculties are impaired.

Field sobriety tests, including the Horizontal Gaze Nystagmus test, the Walk-and-Turn, and the One-Leg Stand, are designed to measure coordination and cognitive function. These tests are standardized by the National Highway Traffic Safety Administration, but they are also highly subjective in practice. Nervousness, fatigue, a medical condition, or even an uneven road surface can produce results that an officer interprets as signs of impairment, even when your BAC is well under the legal limit.

The Role of Drugs in Below-.08% DWI Cases

Texas DWI law covers impairment from prescription drugs, over-the-counter medications, and controlled substances, not just alcohol.

This catches many drivers off guard. If a person’s normal faculties are actually impaired by a prescribed sleep aid, an antihistamine, or an anti-anxiety medication, they can be arrested for DWI regardless of alcohol consumption; the key legal issue is whether the substance actively caused impairment, not simply that the medication was taken before driving. In those situations, a breathalyzer reading is largely irrelevant.

Texas law treats drug-induced impairment the same as alcohol-induced impairment under Penal Code Section 49.01. Drug Recognition Experts, often called DREs, are sometimes brought in to evaluate drivers when officers suspect drug impairment. A drug test may follow, but an arrest can happen before any chemical test results are available.

Why a Low BAC Does Not Equal a Weak Case Against You

Prosecutors can pursue a DWI conviction based on observed impairment alone, making a low BAC result less protective than people expect.

Many people believe that a BAC below .08% is an automatic defense. In reality, it is one piece of evidence among many. A prosecutor can argue that you were impaired based on the officer’s testimony, dashcam footage, field sobriety test results, and witness observations, even if your breath or blood sample came in low.

There is also a method called retrograde extrapolation, which estimates your BAC at the time of driving rather than at the time of testing. However, this forensic concept is highly case-specific and depends heavily on precise timing, drinking patterns, and expert testimony.

A low BAC reading can still be used as part of a strong defense, but it does not dismiss the case on its own. That is exactly why the way your case is built and challenged matters enormously.

What to Do If You Are Arrested for DWI in Bryan

Staying calm, avoiding self-incrimination, and contacting a DWI defense attorney quickly are the most important steps after an arrest.

If you are arrested on suspicion of DWI in Brazos County, even with a BAC that seems well under the limit, take these steps:

• Do not argue with the officer at the scene.
• Invoke your right to remain silent beyond providing your basic identifying information.
• Do not consent to searches beyond what is legally required.
• Contact a Bryan DWI defense attorney as soon as possible after your arrest.

Time matters more than most people realize. Under Texas law, you must request an Administrative License Revocation (ALR) hearing within 15 days of your arrest to contest the suspension; otherwise, under Texas Transportation Code Section 724.035, a refusal can trigger a suspension that takes effect on the 40th day after notice. Missing that window can cost you your license before your criminal case even begins.

Facing a DWI Charge? Shane Phelps Law Is Ready to Help.

A DWI charge with a low BAC is not a case to underestimate, and it is not a situation you should face without someone in your corner who understands how these charges are built and how they can be challenged. At Shane Phelps Law, our criminal defense team has handled DWI cases throughout Bryan and Brazos Counties, and we take every case seriously, regardless of the numbers.

If you or someone you care about has been arrested for DWI, reach out to us today. Call us at 979-596-6843 or contact us to schedule a consultation. Do not wait on the 15-day ALR deadline.