New! AI Legal Avatar — Get 24/7 Answers on Texas DWI Law, Penalties, and Defenses

Our AI Legal Avatar provides instant, plain-language answers to your questions about Texas DWI laws—like penalties, license suspension, and defense strategies—anytime, day or night. While it's a helpful starting point, it doesn't replace the clarity and advocacy of our experienced DWI attorneys.

Do I Need a Texas DWI Attorney?

The consequences of a DWI convictions can extend far beyond the immediate criminal penalties. For a second offense, the consequences multiply. For a third, you are facing a felony.

DWI defense is also a scientific discipline. Most DWI cases involves forensic evidence (a breath test, a blood draw, field sobriety tests, or some combination of all three). Each category of forensic evidence has known methodological limitations, error rates, and conditions under which the results are unreliable. The attorney who challenges that evidence effectively is the one who understands the science behind it, not just the law that governs its admissibility.

Managing Partner Deandra M. Grant holds the ACS-CHAL Forensic Lawyer-Scientist designation, a Master’s Degree in Pharmaceutical Science, a Graduate Certificate in Forensic Toxicology, and is a trained SFST instructor who administers and grades the ACS-CHAL Forensic Lawyer-Scientist and DUIDLA Board Certification exams. Partner Douglas E. Huff holds the same ACS-CHAL designation. DWI forensic science challenges at Deandra Grant Law are conducted at the chemistry level.

What the Science Actually Shows

Breath Testing

The Intoxilyzer 9000 is the breath testing instrument used in Texas. It measures alcohol in deep lung air and converts that measurement to an estimated blood alcohol concentration using a fixed partition ratio of 2100:1. The actual partition ratio varies across the population from approximately 1100:1 to 3400:1. A driver with a partition ratio higher than the assumed 2100:1 will have a lower actual BAC than the test reports. A driver with a partition ratio lower than assumed will have a higher reported BAC than actual.

Beyond the partition ratio issue, breath test results are affected by residual mouth alcohol from recent belching or vomiting (which the 15-minute observation period is intended to control), interfering substances such as isopropanol or acetone in individuals with certain medical conditions, and instrument-specific calibration and maintenance issues. The Intoxilyzer 9000’s calibration records and maintenance logs are part of what the defense obtains and reviews in every breath test case.

Blood Testing

A blood draw provides a direct measurement of blood alcohol concentration, but the result is only as reliable as the collection, storage, and analysis procedures that produced it. Fermentation (the conversion of residual blood sugars to alcohol by bacteria after collection) can occur when specimens are improperly stored or when the sodium fluoride preservative is inadequate or absent. GC-FID (gas chromatography with flame ionization detection) is the standard analytical methodology for blood alcohol analysis. The chromatogram, calibration curve, internal standard performance, and quality control data are all part of what the defense reviews in every blood test case.

Deandra Grant’s pharmaceutical science training applies directly to this analysis. She reviews lab discovery (not just the summary report) and identifies errors and methodological issues that would not be visible to an attorney reviewing only the final number.

Field Sobriety Tests

The three standardized field sobriety tests (the Horizontal Gaze Nystagmus (HGN) test, the Walk and Turn, and the One Leg Stand) were validated by NHTSA in studies conducted under controlled conditions with trained officers. Their accuracy depends entirely on proper administration according to the NHTSA protocol. Deviations from the protocol (in the instruction sequence, the demonstration, the clue observation criteria, or the scoring) undermine the scientific foundation of the results.

Deandra Grant is a trained SFST instructor. She administers and grades the SFST component of the ACS-CHAL Forensic Lawyer-Scientist examination and the DUIDLA Board Certification examination. When she cross-examines an officer about SFST administration, she is doing so from the position of someone who trains and examines other attorneys on the same tests.

Retrograde Extrapolation

In cases where the blood or breath test was administered some time after the traffic stop (or where the question is what the BAC was at the time of driving rather than at the time of testing) the prosecution may attempt to use retrograde extrapolation to project the BAC backward in time. Retrograde extrapolation requires assumptions about the rate of elimination, the absorption phase, and whether the driver was in the absorption or elimination phase at the time of driving. These assumptions are variable across individuals and require pharmacokinetic expertise to challenge effectively. Deandra Grant’s pharmaceutical science training makes this challenge substantive rather than generic.

Areas of Practice

For more information about DWI in Texas, as well as information about our areas of practice as related to DWI defense, please click on the topics below:

• DWI Defense
• Boating While Intoxicated
• CDL DWI
• Intoxication Assault
• Felony DWI
• Hit and Run DWI
• Multiple DWI
• Underage DWI

Deandra Grant Law – Criminal & DWI Defense Helps Residents Across Texas with DWI Defense – Including: Allen , Arlington, Belton, Cleburne, Collin County, Dallas, Denton, Fairview, Fort Worth, Frisco, Gainesville, Granbury, Hood County, Johnson County, Lewisville, Little Elm, McKinney, Park Cities, Parker County, Plano, Princeton, Richardson, Rockwall, Rowlett, Royse City, Southlake, Sunnyvale, The Colony, Waco, and Weatherford.

The ALR Process: Act Within 15 Days

When a Texas driver is arrested for DWI and fails or refuses a breath or blood test, DPS initiates an Administrative License Revocation proceeding. The driver receives a notice of suspension (either at the scene or by mail) and has 15 days from the date of receiving that notice to request an ALR hearing. If no hearing is requested, the suspension takes effect automatically.

Requesting the ALR hearing serves two purposes beyond simply contesting the suspension. It delays the suspension from taking effect while the hearing is pending, which can mean weeks or months of additional driving time. And it compels the arresting officer to appear and testify under oath at a pre-trial hearing, providing the defense an opportunity for sworn cross-examination and fact development before the criminal case is resolved.

If you were arrested for DWI and received a notice of suspension, you have 15 days from the date you received the notice to request the ALR hearing. Contact Deandra Grant Law immediately.

DWI Practice Areas

Each of the following DWI-related practice areas has dedicated sub-page coverage with detailed analysis of the specific legal issues, forensic challenges, and consequences involved:

• Boating While Intoxicated — BWI: the sea legs phenomenon, NHTSA validation gap, TPWD enforcement, ALR applies to driver’s license
• DWI with a CDL — 0.04% threshold, partition ratio forensic challenge at near-threshold BAC, no occupational CDL, personal vehicle DWI triggers disqualification
• DWI with Injury (Intoxication Assault) — §49.07, serious bodily injury definition, causation element, EDR evidence, third-degree felony
• Felony DWI — DWI 3rd (third-degree felony, 2–10 years), pen packet challenges, §49.09(b) peace officer enhancement (first-degree felony), no deferred adjudication, intoxication assault and manslaughter, Bentley’s Law
• Hit and Run DWI — failure to stop and render aid, collision with the DWI charge, evidence preservation issues
• Multiple DWI — enhancement ladder, pen packet challenges, mandatory minimum sentences, look-back period issues
• Underage DWI — §106.041 TABC Class C DUI vs. §49.04 DWI distinction, SFST validation gap for minors, ALR consequences
• Driving Under the Influence of Drugs (DUID) — presence vs. impairment, LC-MS/MS biological specimen analysis, DRE protocol critique

Why Deandra Grant Law for DWI Defense

• ACS-CHAL Forensic Lawyer-Scientist.  Deandra Grant and Douglas Huff are both designated. This credential requires demonstrated competency in the forensic chemistry underlying DWI prosecution. It is not an honorary designation.
• Master’s Degree in Pharmaceutical Science.  Blood alcohol pharmacokinetics, retrograde extrapolation, partition ratio analysis, and GC-FID methodology require this training to challenge effectively.
• Graduate Certificate in Forensic Toxicology.  Forensic evidence interpretation applied to every DWI case.
• Trained SFST Instructor.  
• 30+ years of DWI defense across North and Central Texas.  500+ trials to verdict.
• •  17 published law books. Including The Texas DWI Manual.
• Texas Super Lawyer since 2011.  AV® Preeminent rated by Martindale-Hubbell®.
• Offices in Dallas, Fort Worth, Allen, Denton, Waco, and Rockwall.  North and Central Texas courts served directly.

If you or someone you know has been arrested for DWI in Texas, call (214) 225-7117 for a free, confidential consultation. If you received a notice of suspension, the 15-day ALR deadline is already running. Or schedule online at texasdwisite.com.