Driving While Intoxicated (DWI) remains one of the most aggressively enforced offenses in Texas. As of 2026, Texas DWI law continues to blend long‑standing statutory standards with evolving enforcement practices, technological advances, and constitutional litigation. Understanding how Blood Alcohol Concentration (BAC) fits into the broader DWI framework is critical—not only for drivers, but for anyone facing investigation, arrest, or prosecution.
This article explains how Texas DWI laws work in 2026, with a specific focus on Houston and Harris County enforcement practices, how BAC evidence is used (and often misused), and what legal standards Houston-area law enforcement must meet before a stop, arrest, or conviction can lawfully occur.
1. The Legal Definition of DWI in Texas
Under Texas Penal Code § 49.04, a person commits DWI if they operate a motor vehicle in a public place while intoxicated. Texas law defines intoxication in two distinct—but equally important—ways:
- Loss of normal use of mental or physical faculties due to alcohol, drugs, or a combination of substances; or
- Having a Blood Alcohol Concentration of 0.08% or higher.
Importantly, the State only needs to prove one of these definitions—not both. This means a driver may be arrested and prosecuted even without a breath or blood test showing an unlawful BAC.
2. Reasonable Suspicion and Traffic Stops in Houston DWI Cases
Every DWI case begins with a traffic stop. Under the Fourth Amendment and Texas law, police must have reasonable suspicion that a traffic violation or criminal activity has occurred before stopping a vehicle.
In Houston and throughout Harris County, common reasons officers cite in DWI stops include:
- Speeding or lane deviations
- Failure to maintain a single lane
- Equipment violations
- Reports of erratic driving
At this stage, BAC is not yet part of the equation. The officer is evaluating driving behavior, not intoxication levels. If reasonable suspicion is lacking, all evidence obtained after the stop—including BAC results—may be subject to suppression.
3. From Detention to Investigation: Building Toward Probable Cause
After the stop, an officer may expand the encounter into a DWI investigation if they observe signs suggesting intoxication, such as:
- Odor of alcohol
- Bloodshot or watery eyes
- Slurred speech
- Admissions of drinking
This is typically when field sobriety tests (FSTs) are introduced. These tests are subjective, non‑mandatory, and frequently challenged in court.
At this stage, BAC testing still has not occurred—but the officer is deciding whether there is probable cause to make an arrest and request a breath or blood sample.
4. Blood Alcohol Concentration (BAC) Under Texas Law
BAC plays a central role in DWI prosecutions, but it is often misunderstood by the public.
Legal BAC Thresholds in Texas
Texas law establishes different BAC standards depending on the driver and circumstances:
- 0.08% or higher – Per se intoxication for adult drivers (21 and over)
- 0.04% or higher – Commercial motor vehicle drivers while operating a CMV
- Any detectable amount (0.01% or more) – Zero‑tolerance policy for drivers under 21
A BAC at or above these limits allows the State to argue intoxication without proving loss of normal use.
5. DWI Charges Without a 0.08 BAC
One of the most important aspects of Texas DWI law is that a BAC of 0.08 is not required for a conviction.
A driver may be charged with DWI even if:
- The BAC result is below 0.08%
- No chemical test was taken
- The driver refused testing altogether
In these cases, prosecutors rely on officer observations, FSTs, video footage, and witness testimony to argue loss of normal use. These cases are often more defensible due to their subjective nature.
6. Breath Tests, Blood Tests, and Implied Consent
Texas operates under an implied consent system. By driving on Texas roads, drivers are deemed to have consented to chemical testing after a lawful arrest.
Breath Testing
Breath tests are commonly used but are susceptible to error due to:
- Improper calibration
- Medical conditions
- Operator mistakes
- Environmental factors
Blood Testing
Blood tests are often viewed as more reliable, but they raise serious legal issues involving:
- Search warrants
- Chain of custody
- Lab handling and contamination
- Delays between driving and testing
Courts continue to scrutinize how blood is obtained, stored, and analyzed—especially following warrantless or coerced draws.
7. High BAC Enhancements (0.15 and Above)
Texas law imposes harsher penalties when a driver’s BAC is 0.15% or higher.
A first‑time DWI that would normally be a Class B misdemeanor is enhanced to a Class A misdemeanor, increasing:
- Potential jail time
- Maximum fines
- Probation conditions
Because of the stakes, high‑BAC cases are aggressively litigated, and the accuracy of the testing process becomes critically important.
8. Penalties for DWI in Houston & Harris County (2026)
Penalties vary based on prior offenses, BAC level, and aggravating factors, but may include:
- Jail time
- Heavy fines and court costs
- License suspension
- Ignition interlock requirements
- Alcohol education and treatment programs
Administrative License Revocation (ALR) proceedings—handled locally through the Texas Department of Public Safety offices serving Harris County—run parallel to the criminal case and are heavily tied to BAC testing or refusals.
9. Defending a Texas DWI Case
Effective DWI defense focuses on constitutional violations and scientific weaknesses, including:
- Lack of reasonable suspicion or probable cause
- Improper FST administration
- Unreliable BAC testing
- Illegal blood draws
- Video evidence contradicting officer testimony
BAC evidence is not infallible, and many DWI cases are won or dismissed based on flawed testing or unlawful police conduct.
10. Why Legal Representation Matters Early
DWI cases move quickly, especially when license suspension deadlines are involved. Early representation allows counsel to:
- Demand and preserve evidence
- Challenge BAC procedures
- Contest ALR suspensions
- Position the case for dismissal, reduction, or trial
Houston & Harris County DWI FAQ
Can I be arrested for DWI in Houston without blowing over 0.08?
Yes. In Houston and throughout Harris County, a driver can be arrested and charged with DWI even if their BAC is below 0.08 or no BAC test is taken at all. Prosecutors may rely on officer observations, field sobriety tests, dashcam or bodycam video, and witness testimony to argue loss of normal use.
Should I take the breath test if I’m stopped in Harris County?
There is no one-size-fits-all answer. While refusing a breath or blood test may result in an Administrative License Revocation (ALR), submitting to testing can create powerful evidence for the prosecution. Each situation is different, and the legality of the stop and arrest often determines whether test results can be challenged.
Can Houston police force a blood draw in a DWI case?
Houston-area officers generally must obtain a search warrant to conduct a blood draw unless a legally recognized exception applies. Improper or warrantless blood draws are frequently challenged and may result in suppression of BAC evidence.
What happens to my driver’s license after a DWI arrest in Harris County?
License suspension is handled through a separate ALR process administered by the Texas Department of Public Safety. You have only 15 days from the date of arrest to request an ALR hearing. Missing this deadline can result in automatic suspension.
How long does a DWI case take in Harris County courts?
DWI cases in Harris County often take several months to over a year, depending on court backlog, evidence issues, and whether the case is resolved by dismissal, plea, or trial.
Why should I hire a Houston DWI attorney early?
Early representation allows your attorney to demand video evidence, challenge BAC testing procedures, contest ALR suspensions, and identify constitutional violations before critical deadlines pass.
Final Thoughts for Houston & Harris County Drivers
Texas DWI law in 2026 remains strict, but it is also highly technical. BAC is only one part of a much larger legal puzzle—one that must comply with constitutional protections, statutory rules, and scientific reliability standards.
If you are facing a DWI charge, understanding how BAC fits into your case—and how it can be challenged—may make all the difference.
For informational purposes only. This article does not constitute legal advice.