Waco DUID Lawyers

Texas does not have a separate “DUID” or “drug-DWI” statute. Drug-impaired driving is prosecuted under the same Penal Code § 49.04 that covers alcohol DWI, because the § 49.01(2) definition of “intoxicated” covers alcohol, controlled substances, prescription drugs, and any other substance that causes loss of normal use of mental or physical faculties. The same 0.08 BAC structure does not apply to drugs. There is no per se drug-DWI threshold. The state must prove loss of normal use by reason of the drug.

That makes drug-DWI cases fundamentally different from alcohol-DWI cases. The forensic analysis (LC-MS/MS rather than GC-FID), the standard-of-proof methodology (loss-of-normal-use only, no BAC alternative), the DRE testimony (Drug Recognition Expert opinions with contested reliability), and the prescription-medication context (most drug-DWI cases involve drugs the defendant was entitled to use) all require a distinct defense approach. cases reward.

Deandra Grant Law represents clients facing drug-DWI charges in Waco, Hewitt, Woodway, Bellmead, and throughout McLennan County. Call (254) 735-3588 to discuss your case.

Drug-DWI Is Prosecuted Under Penal Code § 49.04 — Same Statute as Alcohol-DWI

Texas’ DWI statute is Penal Code § 49.04, and its definition of intoxication in § 49.01(2) covers both alcohol and drugs:

• § 49.01(2)(A) — not having 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
• § 49.01(2)(B) — having an alcohol concentration of 0.08 or more.

For alcohol DWI, the state can prove intoxication either way. For drug DWI, only § 49.01(2)(A) applies. There is no per se BAC-equivalent for drugs. The state must prove loss of normal use by reason of the drug. This one-path proof structure is the single most important feature of drug-DWI defense.

What the Statute Covers

The Texas DWI definition of “intoxicated” covers an unusually broad range of substances:

• Alcohol — the traditional DWI context.
• Controlled substances — Penalty Group 1 (cocaine, heroin, meth, opioids), Penalty Group 1-B (fentanyl and analogues), Penalty Group 2 (THC concentrates, hallucinogens), Penalty Groups 3 and 4 (benzodiazepines, barbiturates, certain opioids).
• Dangerous drugs — non-controlled prescription medications under HSC Chapter 483.
• Any other substance — including inhalants, over-the-counter medications, and substances not specifically scheduled but capable of causing impairment.
• Combinations — the most common real-world scenario: alcohol plus a prescription medication, or multiple prescription medications, or illegal drugs plus alcohol.

Importantly, the prosecution does not have to prove the exact substance that caused impairment. They must prove the impairing substance was present and caused loss of normal use. This is both an expansion of the state’s reach and a source of evidentiary vulnerability that can be exploited in defense.

Forensic Analysis — LC-MS/MS and Its Limits

Drug analysis in Texas is typically performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which can identify and quantify specific drug compounds in blood samples. The forensic methodology has several vulnerabilities that defense counsel can investigate:

• Specific drug targeting. LC-MS/MS must be told what compounds to look for. If the lab runs a narrow panel and the actual impairing substance is not on the panel, the state’s case has a gap. Conversely, overbroad panels can identify trace amounts of drugs the defendant took days or weeks earlier.
• Quantification uncertainty. The reported concentration has measurement uncertainty that the lab report often does not disclose. A reported level just above a pharmacological reference range may not support impairment.
• Reference standards. LC-MS/MS depends on comparison to certified reference materials. The calibration, reference lot identity, and method validation data are all contestable.
• Metabolites versus active drug. For many drugs (particularly THC), the blood test detects metabolites that persist long after the drug’s impairing effects have ended. A positive result does not mean the defendant was impaired at the time of driving.
• Chain of custody and storage. Sample handling, storage temperature, and time-to-analysis all affect reliability.

The defense reads the underlying laboratory data packet — chromatograms, mass spectra, QC data, method validation — not just the one-page report. Many drug-DWI cases are won or narrowed at this stage.

Drug Recognition Experts (DREs) and Their Limits

Many Texas drug-DWI cases involve testimony from a Drug Recognition Expert which is a police officer trained in the 12-step DRE evaluation protocol. The DRE is typically called when the arresting officer suspects drug impairment but the subject blows below the alcohol threshold. The 12-step DRE protocol includes pulse, blood pressure, eye examinations (including an assessment for horizontal and vertical nystagmus, and for lack of convergence), muscle tone evaluation, and a psychophysical component.

The DRE methodology is not uncontroverted. Limitations that effective cross-examination can expose:

• The DRE conducts the evaluation after arrest which typically means the subject has already been detained and is under substantial stress, affecting many of the physiological measures.
• The DRE protocol has not been validated against the actual question in a criminal case (whether the subject was impaired at the time of driving).
• DRE training is a 2- to 3-week certification, which is modest professional credentialing for the diagnostic claim being made.
• The protocol’s reliability varies substantially by drug category. DRE accuracy for some categories (e.g., cannabis) is particularly contested.
• The DRE’s field impression is then confirmed or not confirmed by a blood test. When the blood test confirms the DRE’s impression, the state argues reliability. When the blood test disagrees, the state sometimes argues the test was taken too late or at the wrong window (but this is also an admission that DRE alone cannot reliably identify impairment).

Prescription Medication — Most Drug-DWI Cases

A substantial fraction of drug-DWI cases in Texas involve prescription medication (opioids, benzodiazepines, muscle relaxants, sleep aids, ADHD medications, or combinations) taken as prescribed. Under Penal Code § 49.10 the fact that the defendant was entitled to use the drug under a prescription is not a defense to DWI. The legality of possession is separate from the DWI question of whether the drug caused loss of normal use.

However, prescription context significantly affects the defense. When the defendant has a therapeutic relationship with a prescribing physician, a history of stable medication use at the same dosage, and no evidence of recent dose changes or misuse, the loss-of-normal-use analysis becomes much harder for the state. Medical records, prescribing-physician testimony, and pharmacology expert testimony can materially shift the evidentiary picture.

THC and the Hemp Complication

Since HB 1325 (2019), Texas has legalized hemp (cannabis containing 0.3% or less delta-9 THC). This has created a complex framework for drug-DWI cases involving THC:

• A positive THC blood test does not distinguish between legal hemp consumption and illegal marijuana use.
• THC has a long metabolic half-life, with detectable metabolites remaining in blood for days or weeks after last use.
• The relationship between blood THC concentration and impairment at the time of driving is contested in the scientific literature. There is no well-validated “THC threshold” for impairment comparable to the 0.08 BAC threshold for alcohol.
• Chronic cannabis users can have detectable THC in blood for weeks after last use without acute impairment.

For Waco DWI cases involving THC (including cases arising from hemp-product consumption, medical cannabis use in other states, or legal CBD with trace THC) the scientific challenges to a THC-based impairment claim are substantial.

When a Drug-DWI Becomes a Felony

Drug-DWI is a misdemeanor on the first offense: Class B misdemeanor at baseline, Class A misdemeanor if the 0.15 BAC threshold is met (which typically applies only when alcohol is also involved). The felony-DWI categories apply to drug cases the same way they apply to alcohol cases:

• Third or subsequent DWI — § 49.09(b)(2), third-degree felony.
• DWI with Child Passenger — § 49.045, state jail felony.
• Intoxication Assault — § 49.07, third-degree felony (second-degree if peace officer, firefighter, or EMS victim, or if TBI).
• Intoxication Manslaughter — § 49.08, second-degree felony (on the 3g list, no judge-granted probation).

Collateral Consequences

• Driver’s license suspension. DWI conviction carries a 90-day-to-1-year suspension under Transportation Code § 521.344. Drug convictions (which may or may not be charged alongside the DWI) carry a separate 180-day suspension under § 521.372 (1 year if under 21).
• Ignition interlock under CCP Article 17.441, when BAC 0.15+ is involved or on repeat offenses.
• Federal firearm prohibition on any felony conviction under 18 U.S.C. § 922(g)(1); Texas prohibition under Penal Code § 46.04(a).
• Immigration consequences. Drug convictions (other than small-quantity marijuana) are deportable offenses under 8 U.S.C. § 1227(a)(2)(B).
• Professional licensing. Nursing, teaching, pharmacy, medicine, and other Texas licensing boards conduct separate proceedings after DWI or drug convictions.
• Auto insurance. Premium increases on DWI convictions are substantial.
• Employment. DWI convictions (and particularly drug-DWI convictions) appear on background checks and affect employment opportunities.

How Drug-DWI Cases Are Defended

Challenging the Loss-of-Normal-Use Showing

Without a BAC-equivalent threshold for drugs, the state’s case depends entirely on proving loss of normal use by reason of the drug. Where the observational evidence (dash cam, body cam, field sobriety video, booking video) is inconsistent with impairment, the case can often be reduced or dismissed.

Forensic Attack on the Blood Test

LC-MS/MS analysis has many attack points: chain of custody, panel scope, quantification uncertainty, reference standard reliability, metabolite versus parent drug interpretation, and storage/handling effects.

DRE Cross-Examination

DREs are police officers, not medical professionals. Effective cross-examination on the scientific limits of the DRE methodology, the officer’s specific training and experience, inconsistencies between the DRE’s impression and the blood test results, and the bias inherent in post-arrest evaluation can undermine DRE testimony.

Prescription Context Development

Medical records, pharmacy records, prescribing-physician testimony, and pharmacology expert testimony can establish that the defendant was using the medication as prescribed with no acute change in dose or use pattern, undermining the state’s impairment theory.

Fourth Amendment and CCP Art. 38.23

Stops, field sobriety testing, arrests, and blood warrants are subject to constitutional review. Drug-DWI cases often involve consent-based blood draws that can be challenged on consent validity.

THC-Specific Defense

For THC-involving cases, attacking the relationship between a positive THC test and impairment at the time of driving is often the defense’s strongest ground.

Where McLennan County Drug-DWI Cases Are Heard

First-offense misdemeanor drug-DWI cases in McLennan County are filed in the McLennan County Courts at Law. Felony drug-DWI cases (repeat, child passenger, intoxication assault, intoxication manslaughter) are filed in the McLennan County District Courts at the McLennan County Courthouse, 501 Washington Avenue, Waco. The McLennan County District Attorney’s Office prosecutes all criminal cases in McLennan County.

Frequently Asked Questions

Is there a separate “DUID” statute in Texas?

No. Drug-impaired driving is prosecuted under the same Penal Code § 49.04 that covers alcohol DWI. The § 49.01(2) definition of “intoxicated” includes drugs, controlled substances, dangerous drugs, combinations, and any other impairing substance.

Is there a BAC-equivalent for drugs?

No. There is no per se drug-DWI threshold in Texas. The state must prove loss of normal use by reason of the drug. Without a threshold, the state’s case depends on observational and forensic evidence of impairment, which can be contested in ways alcohol BAC cases cannot.

I had a valid prescription. Is that a defense?

Not directly. Under Penal Code § 49.10, a valid prescription is not a defense to DWI. However, the prescription context often shifts the loss-of-normal-use analysis. A defendant with a stable therapeutic relationship, consistent dosing history, and no evidence of misuse presents a materially different case than the “recreational drug” profile the state’s case sometimes assumes.

The officer wasn’t a doctor. Can they testify I was impaired?

Yes, within limits. Arresting officers can testify to observable signs of impairment. Drug Recognition Experts (DREs) can testify to their DRE protocol findings. The weight of this testimony is a defense target. The DRE methodology is not as well-validated as the state sometimes suggests, and cross-examination of DRE officers frequently undermines the opinion.

What if my test was just for THC?

THC cases have special complications. HB 1325 (2019) legalized hemp (cannabis with 0.3% or less delta-9 THC), so a positive THC test does not distinguish between legal and illegal consumption. THC’s long metabolic half-life means detectable blood levels can persist for days or weeks after last use, and the relationship between blood THC concentration and actual impairment is contested in the scientific literature. These factors make THC-based drug-DWI prosecutions substantially harder for the state.

Can my drug-DWI become a felony?

Yes, under the same rules as alcohol DWI. A third-or-subsequent DWI is a third-degree felony under § 49.09(b)(2). DWI with a Child Passenger is a state jail felony under § 49.045. Intoxication Assault is a third-degree felony under § 49.07. Intoxication Manslaughter is a second-degree felony under § 49.08 (on the 3g list, with no judge-granted probation available). And under the HB 6 fentanyl murder provision, a drug-DWI case involving fentanyl that results in death can become a first-degree felony murder prosecution.

About Deandra Grant Law

Deandra Grant Law is a Texas criminal defense firm with offices in Waco, Dallas, Fort Worth, Allen, Denton, and Rockwall. Our DWI practice is particularly deep on the drug-DWI side where the forensic training and the challenge to the state’s impairment theory matter most.

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
• AV Preeminent rated by Martindale-Hubbell
• Executive Director, DUI Defense Lawyers Association (DUIDLA)

Douglas E. Huff, Partner

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

James Lee Bright, Of Counsel

• National federal criminal defense practice
• Admitted to all four Texas federal districts (including the Western District of Texas, which covers McLennan County), the District of Columbia, the Fifth Circuit Court of Appeals, and the Supreme Court of the United States

Contact Our Waco DUID Attorneys

Drug-DWI cases reward forensic training more than any other DWI category. The state has no BAC-equivalent threshold; its case depends on observational evidence, DRE testimony, and LC-MS/MS results (each of which is contestable with the right preparation). The firm that handles drug-DWI cases the way it handles alcohol cases will miss the specific defenses available. The firm that understands the forensic chemistry of LC-MS/MS, the pharmacology of prescription medications, the limits of the DRE protocol, and the scientific gaps in THC impairment testing will often produce dramatically different outcomes.

Call Deandra Grant Law at (254) 735-3588 to schedule a consultation. We serve Waco, Hewitt, Woodway, Bellmead, and all of McLennan County from our Waco office.