Denton DUID Lawyers

A drug DWI in Texas is still a DWI. There is no separate “DUID” statute. Texas Penal Code § 49.04 covers alcohol, drugs, and everything in between. But drug DWI cases operate differently at the forensic and investigative level than alcohol cases. There is no per se drug limit the way there is a 0.08 BAC. The state relies on blood toxicology, Drug Recognition Evaluations, and circumstantial evidence to prove impairment. And because many drugs produce metabolites that linger long after the psychoactive effects have ended, the gap between what the lab report says and what actually happened on the road is often larger than the state’s case suggests.

Deandra Grant Law represents clients facing drug-based DWI charges in Denton County. Call (214) 225-7117 to discuss your case.

“DUID” Is Not a Separate Texas Offense

Some states have distinct “driving under the influence of drugs” statutes. Texas does not. Texas has one DWI statute that covers every form of intoxication.

Under Penal Code § 49.01(2), a person is “intoxicated” when the person:

• Does 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, or a combination of two or more of those substances, or any other substance into the body; or
• Has an alcohol concentration of 0.08 or more.

In a drug DWI case, the state almost always proceeds on the first prong which means loss of normal faculties by reason of a drug. The second prong (0.08 BAC) doesn’t apply, and there is no drug-based equivalent under Texas law.

Texas Has No Per Se Drug Limit

For alcohol, Texas law fixes a number: 0.08 grams per 100 milliliters of blood or 210 liters of breath is “intoxicated” as a matter of law, regardless of whether the particular driver could actually handle that level of alcohol. The number is the element.

For drugs, there is no such number. No nanogram-per-milliliter threshold of THC, no micrograms per liter of alprazolam, no concentration of cocaine metabolites triggers automatic DWI liability. The state must prove actual impairment (loss of normal use of mental or physical faculties) in every drug DWI case. A detectable drug level in the blood is evidence the state tries to use; it is not itself the offense.

What Counts as a “Drug” in a Drug DWI

The statute reaches any substance that causes impairment, whether or not it is illegal. Drug DWI cases in Denton County arise from:

• Prescription medications — benzodiazepines (Xanax, Valium, Klonopin), opioids (Vicodin, Oxycontin, hydrocodone), sleep aids (Ambien), muscle relaxants (Soma, Flexeril), and stimulants (Adderall, Ritalin). A valid prescription is not a defense under Penal Code § 49.10.
• Marijuana and THC products. Active THC metabolites are the state’s usual evidence; the relationship between blood THC level and impairment is scientifically contested.
• Cocaine and cocaine metabolites. Benzoylecgonine is an inactive metabolite that persists far beyond impairment.
• Methamphetamine, MDMA, and other stimulants. Differentiation from legal prescription amphetamines is a recurring forensic issue.
• Heroin, fentanyl, and other opioids.
• Over-the-counter medications (antihistamines, cold medicines, sleep aids) — the statute applies to any substance causing impairment.
• Combinations of alcohol and drugs, which are prosecuted as combined-substance DWI under the same § 49.04 framework.

The Prescription Defense Problem — Penal Code § 49.10

Clients with valid prescriptions often assume that prescription status is a defense. Texas Penal Code § 49.10 specifically forecloses that argument: the fact that the defendant had a valid prescription is not a defense to DWI. The question is whether the state can prove that the defendant was actually impaired, not whether the defendant was legally permitted to take the medication.

The prescription status does matter at other points: it goes to the defendant’s state of mind, it may support mitigation at sentencing, and it can open the door to alternative sentencing. But it does not defeat the state’s case.

How the State Builds a Drug DWI Case

Traffic Stop and Investigation

A drug DWI investigation typically begins with a traffic stop for a driving violation (ex. speeding, lane deviation, a stoplight violation, or a more ambiguous “erratic driving” indicator). The officer then looks for signs of impairment: bloodshot eyes, slurred speech, slow responses, pupil size, odor, and driving behavior. When the officer does not smell alcohol but sees signs of impairment, the case becomes a drug DWI investigation.

Field Sobriety Testing

The standard Standardized Field Sobriety Test battery (HGN, walk-and-turn, one-leg stand) was validated for alcohol impairment, not drug impairment. Officers administer them in drug DWI cases anyway with known limitations. Horizontal gaze nystagmus (HGN), for example, is not typically caused by cannabis or stimulants; the presence or absence of HGN is diagnostic in alcohol cases but not in drug cases.

Drug Recognition Evaluation (DRE)

When a DRE-certified officer is available, a 12-step Drug Recognition Evaluation is typically conducted. The DRE protocol was developed by the International Association of Chiefs of Police (IACP) and includes:

• Breath alcohol test (to rule out alcohol-only impairment).
• Interview of the arresting officer.
• Preliminary examination and first pulse.
• Eye examinations (HGN, vertical gaze nystagmus, lack of convergence).
• Divided attention tests (modified Romberg, walk-and-turn, one-leg stand, finger-to-nose).
• Vital signs (blood pressure, temperature, second pulse).
• Dark room examinations (pupil size under three lighting conditions, oral and nasal cavity examination).
• Muscle tone examination.
• Examination for injection sites and third pulse.
• Subject’s statements and other observations.
• Officer’s opinion of drug category.
• Toxicological examination (blood or urine collection for lab analysis).

DRE opinions are contestable on multiple grounds: the officer’s training and currency, administration errors in the individual components, the scientific validity of certain DRE elements, and the ultimate opinion about drug category.

Toxicology

After arrest, the state obtains a blood sample either by consent, by warrant, or under Transportation Code § 724.012 in qualifying cases. The blood is sent to a DPS laboratory or, in some cases, a private lab for analysis. Drug confirmation uses liquid chromatography–tandem mass spectrometry (LC-MS/MS), the forensically appropriate technique for the low concentrations typical of drug DWI cases. The state’s lab report becomes the centerpiece of the prosecution.

How Drug DWI Cases Are Defended

Toxicology and Lab Packet Analysis

The one-page lab report the prosecutor hands over on a drug DWI case is not the evidence. The evidence is the full underlying data packet (the chromatograms, the mass spectra, the reference standard comparisons, the calibration data, the quality control results, and the analyst’s worksheet). Errors in internal standard calibration, column contamination, reference standard lot validity, and mass accuracy can render a result unreliable.

Active vs. Inactive Metabolites

Many drugs produce metabolites that persist in blood and urine for days or weeks after the psychoactive effects have ended. Benzoylecgonine (cocaine metabolite), carboxy-THC (cannabis metabolite), and similar compounds are evidence of past use but not present impairment. A drug DWI case built on inactive metabolites, without evidence of active psychoactive compound, is legally and scientifically weak.

DRE Challenges

Drug Recognition Evaluations are systematically conducted but not always correctly conducted. Pulse rate measurement errors, incorrect pupil-size estimation, improper HGN administration, and departures from the IACP protocol are regular defense findings. Many components of the DRE (including the claim that pupil size reliably indicates drug category) have been criticized in the scientific literature.

Blood Draw and Warrant Challenges

Post–Missouri v. McNeely, 569 U.S. 141 (2013), warrantless nonconsensual blood draws are unconstitutional absent an exception. Denton County officers typically secure a search warrant under CCP Article 18.01 after a refusal, working from a standard boilerplate probable cause affidavit. The affidavit’s particularity, the probable cause it actually contains, the execution of the warrant, and the manner of the draw are all contestable.

Prescription-Specific Defenses

For prescription medication cases, the defense focuses on whether the state can actually prove impairment as opposed to mere detection. Pharmacokinetic modeling, the therapeutic range of the medication, individual tolerance, and the timing between last dose and driving can all contradict the state’s impairment theory.

Constitutional Challenges

Traffic stops, field sobriety investigations, arrests, and warrant applications are all subject to the Fourth Amendment and Article 38.23 of the Code of Criminal Procedure. Suppression motions attacking the stop, the scope of the detention, the probable cause for arrest, and the warrant are routine in drug DWI defense.

Punishment for Drug DWI — Same as Any DWI

Drug DWI punishment follows the same § 49.04 / § 49.09 / § 49.045 / § 49.07 / § 49.08 framework as alcohol DWI. In summary:

• First-offense drug DWI. Class B misdemeanor. 72 hours to 180 days in county jail, fine up to $2,000, 90-day to 1-year driver’s license suspension. HB 3582 deferred adjudication may be available if the case is not a felony and not a BAC-0.15 case.
• First-offense drug DWI with BAC 0.15 or above (for combined drug-and-alcohol cases). Class A misdemeanor. Up to 1 year county jail, fine up to $4,000, mandatory interlock under CCP Article 17.441.
• Drug DWI second. Class A misdemeanor. 30-day mandatory minimum jail time under § 49.09(a), 72 hours of which is non-probatable.
• Drug DWI third or subsequent. Third-degree felony. 2 to 10 years in TDCJ. Texas has no “lookback”. Any prior DWI conviction at any age counts.
• Drug DWI with child passenger under § 49.045. State jail felony on a first offense.
• Intoxication assault under § 49.07 (drug-caused serious bodily injury). Third-degree felony; 2 to 10 years, 160 to 600 hours community service. Enhanced to second-degree for peace officer / firefighter / EMS victims or for traumatic brain injury with persistent vegetative state.
• Intoxication manslaughter under § 49.08 (drug-caused death). Second-degree felony; 2 to 20 years, 240 to 800 hours community service. Enhanced to first-degree for peace officer / firefighter / EMS victims.
• HB 2630 / Transportation Code § 709.001 state fines on conviction ($3,000 for a first DWI, $4,500 for a second-within-36-months, $6,000 for BAC 0.15 or above), in addition to the criminal fine.

Administrative License Revocation (ALR)

Drug DWI arrests trigger the same ALR framework as alcohol DWI arrests, with a 15-day deadline from the notice of suspension to request a hearing. A refusal of a blood draw triggers a 180-day ALR suspension on a first refusal and a 2-year suspension on a repeat. Requesting the ALR hearing is almost always the right call because it produces an opportunity to cross-examine the arresting officer under oath before the criminal case is tried.

Where Denton County Drug DWI Cases Are Heard

Misdemeanor drug DWI cases are filed in the Denton County Criminal Courts. Felony drug DWI cases (DWI 3rd, DWI with child passenger, intoxication assault, intoxication manslaughter) are filed in the Denton County Criminal District Courts. Both sit at the Denton County Courts Complex, 1450 E. McKinney Street, Denton. The Denton County Criminal District Attorney’s Office prosecutes.

Frequently Asked Questions

I had a valid prescription. Is that a defense?

No. Texas Penal Code § 49.10 specifically forecloses the “I had a prescription” defense. The state must prove actual impairment, not illegality of possession. Prescription status matters at other points (sentencing, alternative resolutions, mitigation) but it does not defeat the DWI charge itself.

What drug level equals intoxication in Texas?

There is no per se drug threshold in Texas. Unlike the 0.08 BAC limit for alcohol, no concentration of any drug automatically equals intoxication as a matter of law. The state must prove actual impairment in every drug DWI case.

I smoked marijuana yesterday, not when I was driving. Can I still be charged?

You can be charged, but the case is scientifically contestable. Carboxy-THC, the inactive metabolite of THC, persists in blood and urine long after psychoactive effects have ended. A case built on metabolite detection without evidence of active THC (or without observations supporting impairment at the time of driving) is weak.

Can the police make me give a blood sample?

Not without consent, a warrant, or a statutory exception. Texas officers typically obtain a search warrant under CCP Article 18.01 after refusal. The warrant, the affidavit, and the manner of the draw are all contestable.

What’s the difference between a DUID case and an alcohol DWI case?

Legally, they are the same offense (Penal Code § 49.04). Factually, the evidence is different. Alcohol cases rely on breath or blood alcohol concentration and the 0.08 per se limit. Drug cases rely on blood toxicology, Drug Recognition Evaluations, and circumstantial evidence of impairment. The defense framework is tailored accordingly.

About Deandra Grant Law

Deandra Grant Law is a Texas criminal defense and DWI firm with offices in Denton, Dallas, Fort Worth, Allen, Waco, and Rockwall. Our drug DWI practice is built on the forensic training that these cases actually require.

Deandra M. Grant, Managing Partner

• More than 30 years in practice, focused on criminal defense and DWI
• Former prosecutor
• J.D.; M.S. in Pharmaceutical Sciences
• Graduate Certificate in Forensic Toxicology
• ACS-CHAL Forensic Lawyer-Scientist from the American Chemical Society
• Standardized Field Sobriety Test (SFST) Instructor
• DRE Training
• Texas Super Lawyer since 2011
• Author of 17 law books including The Texas DWI Manual
• Executive Director, DUI Defense Lawyers Association (DUIDLA)

Douglas E. Huff, Partner

• ACS-CHAL Forensic Lawyer-Scientist
• Digital forensics and electronic evidence training
• Extensive DWI trial experience across North Texas

James Lee Bright, Of Counsel

• National federal criminal defense practice
• Admitted to all four Texas federal districts, the District of Columbia, the Fifth Circuit Court of Appeals, and the Supreme Court of the United States

Contact Our Denton DUID Attorneys

Drug DWI cases are won on the science. Blood draws happen once; toxicology reports contain far more data than the one-page summary; DREs are documented on standardized forms that reflect the officer’s training and performance. The decisions made in the first weeks after arrest (whether to re-test the blood sample, whether to preserve specific surveillance video, how to prepare for the ALR hearing) often determine the result of the case.

Call Deandra Grant Law at (214) 225-7117 to schedule a consultation. We serve Denton County and surrounding North Texas counties from our Denton office.