Can You Be Arrested for DWI in Texas Under 0.08 BAC?

The question: Can I be arrested for DWI in Texas if my BAC is under 0.08?

The short answer: Yes. The 0.08 blood alcohol concentration limit is one way Texas defines intoxication but it is not the only way. Under Texas Penal Code §49.01, a person is also intoxicated if they have lost the normal use of their mental or physical faculties due to the introduction of alcohol, drugs, or any other substance. That means an officer can arrest, and a prosecutor can charge, a person whose BAC is below 0.08 (or a person who has not been tested at all) if the officer believes the loss-of-faculties standard has been met. This is the prong of Texas DWI law that surprises defendants the most, and it is the prong that drives many of the most contestable DWI prosecutions in the state.

Here is the longer answer: what §49.01 actually says, how the loss-of-faculties standard works, and why a sub-0.08 reading does not end a DWI investigation in Texas.

The Texas Definition of Intoxication

Texas Penal Code §49.01(2) defines “intoxicated” in two ways. A person is intoxicated if they:

(A) do not have 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 two or more of those substances, or any other substance into the body, or
(B) have an alcohol concentration of 0.08 or more.

Both definitions are independently sufficient. The State does not have to prove both. The State has to prove either one. That structure is the key to understanding how a person can be arrested and prosecuted for DWI even with a BAC under 0.08.

The 0.08 prong (known as the per-se prong) is the one most people know about. The loss-of-faculties prong (known as the impairment prong) is the one that catches defendants by surprise. Both have been part of Texas DWI law for decades. Both are charged regularly. And in cases where the chemical evidence is weak, the impairment prong is often where the State plants its flag.

How an Under-0.08 Arrest Actually Happens

Several common scenarios produce a DWI arrest with a BAC below 0.08:

Low-BAC arrest based on roadside performance. A driver blows a 0.06 on a portable breath test, performs poorly on field sobriety tests, and the officer arrests on the loss-of-faculties theory. The lab confirms the sub-0.08 result, and the case proceeds on the impairment prong.
Drug-only DWI. A driver who has used cannabis, prescription medication, or any other substance can be charged with DWI under §49.01 even with a BAC of 0.00. Texas has no per-se drug limit so the entire prosecution rests on the loss-of-faculties theory.
Combination cases. A driver who has consumed alcohol and a drug (even a legal one) may have a low BAC but be charged on the theory that the combination produced loss of faculties.
Refusal cases without test results. If a driver refuses a breath or blood test and the State cannot obtain a warrant, there may be no chemical evidence at all. The case proceeds entirely on observational and behavioral evidence under the loss-of-faculties theory.
Rising-BAC cases. In cases where the BAC at the time of the test is above 0.08 but the defense can argue the BAC was lower at the time of driving, the State may shift to the loss-of-faculties theory to avoid the timing problem.

In all of these scenarios, the absence of a 0.08 reading does not protect the defendant. The State is permitted to argue intoxication based on what the officer observed and what the witnesses describe, and it does so regularly.

What “Loss of Normal Use of Faculties” Actually Means

The phrase is intentionally broad. Texas courts have not defined it as a precise medical or scientific concept. It is a question for the jury, given general guidance about the ordinary meaning of the words. “Mental faculties” refers to the ability to think, perceive, judge, and react. “Physical faculties” refers to the ability to control the body: balance, coordination, motor function, speech.

In practice, the State proves loss of faculties through:

Driving behavior. Weaving, speeding or excessively slow driving, failure to maintain a lane, missing a stop sign, hitting a curb, accidents.
Officer observations. Bloodshot eyes, slurred speech, the odor of alcohol, fumbling for documents, unsteady balance, confused responses.
Field sobriety test performance. Officer-scored “clues” on HGN, walk-and-turn, and one-leg stand.
Statements by the defendant. Admissions of drinking, statements about the night, anything inconsistent with normal mental functioning.
Witness testimony. Bartenders, passengers, other drivers, anyone who saw the defendant before or during the incident.
Chemical evidence, if available. Even a sub-0.08 reading is corroborative evidence. It confirms alcohol consumption, even if it does not establish per-se intoxication.

This is why the State does not need a 0.08 to prosecute. A motivated prosecutor can build an impairment case from observation and testimony alone. They do, or attempt to, in cases where the chemical evidence is weak or absent.

Why the Impairment Prong Is Defendable

The good news for defendants is that the impairment prong is, in many ways, more contestable than the per-se prong. Where the per-se prong relies on a number that has the appearance of objectivity, the impairment prong relies on subjective observations that have well-known reliability problems. A real defense addresses each category:

Driving behavior. Lane drift can be caused by texting, fatigue, distraction, mechanical issues, or weather and not just intoxication. Witnesses, dashcam footage, and the timing of any observed driving can all be developed.
Officer observations. Bloodshot eyes can come from allergies, contact lenses, lack of sleep, or crying. Slurred speech can be a natural speech pattern, anxiety, or a medical condition. The odor of alcohol indicates consumption but not impairment. Fumbling for documents at 2 a.m. with flashing lights in your face is not unusual for sober drivers.
Field sobriety test performance. Addressed in detail in our SFST post. Conditions, age, weight, footwear, medical conditions, and administration errors all confound performance.
Defendant statements. Statements obtained without proper Miranda warnings or in coercive circumstances may be subject to suppression. Statements that were elicited through casual conversation are subject to challenge on voluntariness grounds.
The chemistry. A sub-0.08 result, even if introduced, is consistent with someone who had a drink but not necessarily someone whose faculties were lost. A defense expert can put the number in context.

Because the impairment prong relies on subjective observation, it lives or dies on the credibility of the officer’s narrative. That narrative is almost always testable against video evidence, medical records, and physical reality.

Drug DWI Without Alcohol: The DUID Problem

Texas does not have a per-se drug limit. Unlike some states that set numerical thresholds for THC, certain prescription drugs, or controlled substances, Texas requires the State to prove loss of faculties for any drug-related DWI prosecution. That structural choice has practical consequences:

A positive drug test alone is not enough. A blood test showing a metabolite of cannabis, for example, proves prior use but not impairment at the time of driving. The State has to prove the loss-of-faculties prong independently.
DRE evaluations are observational. Drug Recognition Evaluator assessments produced by trained officers are observational evidence subject to the same kinds of challenges as field sobriety tests. They are not chemical evidence.
Chronic users present specific issues. Drugs like cannabis are stored in body fat and released over time. A regular user can test positive days or weeks after their last use, with no current impairment whatsoever. The State has to prove the impairment was contemporaneous with the driving and not historical.
Prescription medications. A driver taking prescribed medications as directed can still be charged with DWI if the State alleges the medication caused loss of faculties. “I took my prescription as directed” is not a complete defense but it is the foundation of one.

DUID cases are some of the most forensically and legally complex DWI prosecutions in Texas. They require a defense lawyer who understands both pharmacology and the loss-of-faculties standard.

Combination Cases: Alcohol Plus Something Else

The combination prong of §49.01 is increasingly common. The statute explicitly contemplates intoxication caused by “a combination of two or more of those substances” (ex. alcohol plus drugs, alcohol plus medication, drugs plus medication). In a combination case:

The BAC may be low. 04, 0.05, 0.06 — well below the per-se limit on alcohol alone.
The drug or medication may be lawful. A prescribed medication, an over-the-counter cold medicine, or a controlled substance with a valid prescription.
The State’s theory is that the combination produced loss of faculties. The defense response often involves toxicology expertise, pharmacokinetic analysis of the specific substances at the specific concentrations measured, and challenge to the State’s assumption that any detectable level produced impairment.

Generic DWI defense rarely produces good outcomes in cases that turn on combined-substance pharmacology.

Under-21 Drivers: A Different Standard Entirely

If you are under twenty-one, the framework changes again. Texas has a zero-tolerance approach to drivers under twenty-one. Under Penal Code §106.041, a minor who operates a motor vehicle in a public place with any detectable amount of alcohol in the system commits the offense of Driving Under the Influence (DUI) by a Minor which is a Class C misdemeanor. “Detectable” means any measurable amount so not 0.08, not 0.04, but anything above the lower limit of detection of the testing instrument.

This is why the under-21 DUI is fundamentally different from the adult DWI. Adult DWI requires either 0.08 or loss of faculties. Minor DUI requires only that any alcohol be detectable. A driver under twenty-one can be charged with DUI for a BAC well below 0.08 and, depending on the specific facts, may be charged with DWI under §49.04 if the State believes there was loss of faculties or a BAC of 0.08 or above.

The interaction between minor DUI and adult DWI is covered in detail in separate Knowledge Vault Blog posts here and here. The point for purposes of this post is that the 0.08 threshold is even less protective for under-21 drivers than for adults.

Why People Believe 0.08 Is the Magic Number and Why That’s Wrong

Public education about DWI tends to focus on the 0.08 number because it is concrete and quotable. “Don’t drive over 0.08” fits on a poster. “Don’t drive impaired by alcohol, drugs, or any combination thereof under the totality of circumstances” does not.

The result is a widespread belief that staying under 0.08 means you’re safe from DWI prosecution. That belief is wrong, and it gets people arrested. Officers know about the impairment prong. Prosecutors charge cases under it. Juries can convict on it. Anyone who relies on a sub-0.08 reading as a defense is relying on only half of the statute.

The Bottom Line

You can be arrested for DWI in Texas with a BAC below 0.08 or with no test result at all. The 0.08 limit is one way to prove intoxication. The loss-of-normal-use-of-faculties standard is the other, and it does not require a chemical test. Drug DWIs, prescription-medication cases, combination cases, and refusal cases are all routinely prosecuted on the impairment prong. The defense to a sub-0.08 prosecution is not the chemical number. It is a forensic, observational, and procedural challenge to the State’s theory of impairment. It is winnable, but it requires a defense lawyer who understands what the statute actually says and how the State actually charges these cases.

DWI Defense at Deandra Grant Law

Deandra Grant Law defends DWI and intoxication-offense cases across North and Central Texas including Dallas, Fort Worth, Plano, McKinney, Frisco, Allen, Lewisville, Denton, Rockwall, and Waco. We handle the full spectrum of DWI cases (per-se prosecutions, loss-of-faculties prosecutions, drug DWIs, combination cases, and refusal cases) and we apply forensic and pharmacological analysis to every one of them. Our team includes an ACS-CHAL Forensic Lawyer-Scientist with a Master of Science in Pharmaceutical Science and a Graduate Certificate in Forensic Toxicology which are the credentials required to challenge DWI evidence at the level of the science.

If you have been arrested for DWI in Texas with a BAC under 0.08, with no test at all, or in a drug or combination case, call Deandra Grant Law at (214) 225-7117 or visit texasdwisite.com to schedule a confidential consultation. And remember: the 15-day ALR deadline runs from the date of service of the notice of suspension.

Have a DWI question you want answered in this series? Submit it at texasdwisite.com — you might see it featured in a future Ask Deandra post.