Cannabis Driving Impairment Laws in Texas
How Texas defines, charges, and prosecutes driving under the influence of cannabis, including the lack of a per se THC limit.
Texas has no THC blood-level cutoff for driving — unlike alcohol's 0.08 BAC, impairment by cannabis is judged by an officer's observations and a prosecutor's argument. That means a DWI charge can rest on field sobriety performance, the smell of cannabis, admissions, and any detectable THC in blood. Refusing a blood draw triggers automatic license suspension under implied consent. The system gives police and prosecutors wide discretion, and outcomes vary heavily by county.
Not legal advice
This article is informational and is not legal advice. Laws change, prosecutors interpret them differently, and individual cases turn on facts. If you are facing a charge or planning conduct that could trigger one, consult a licensed Texas attorney. Information here was last verified June 2024.
The basic statute
Texas does not have a separate "drugged driving" statute. Cannabis-impaired driving is prosecuted under the general DWI law, Texas Penal Code §49.04, which makes it an offense to operate a motor vehicle in a public place while "intoxicated" [1].
"Intoxicated" is defined in §49.01(2) as either:
- 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
- having an alcohol concentration of 0.08 or more [2].
The 0.08 prong is alcohol-only. For cannabis, the prosecution must prove loss of normal use of mental or physical faculties — a subjective standard. Strong evidence
No per se THC limit
Unlike Colorado (5 ng/mL THC permissible inference) or Washington (5 ng/mL per se), Texas has no numeric THC threshold in statute [3]. A driver can be convicted with any detectable THC if the state proves loss of normal use, and can theoretically be acquitted with high THC blood levels if the defense rebuts the impairment evidence.
This matters because THC pharmacokinetics don't track impairment the way alcohol does. Blood THC drops quickly after smoking even while psychoactive effects persist, and chronic users can have measurable THC days after last use without acute impairment [4]. Strong evidence Texas's standard sidesteps that mismatch but replaces it with officer discretion.
How cases get built
A typical cannabis DWI in Texas develops like this:
- Traffic stop for an unrelated violation (speed, lane, equipment).
- Officer observations: odor of marijuana, red eyes, slow speech, admissions.
- Standardized Field Sobriety Tests (SFSTs): walk-and-turn, one-leg stand, horizontal gaze nystagmus. SFSTs were validated for alcohol; their accuracy for cannabis impairment is weaker and contested in the research literature [5]. Disputed
- Drug Recognition Expert (DRE) evaluation if available — a 12-step protocol. NHTSA endorses DRE evaluations, but peer-reviewed studies show variable accuracy [6]. Weak / limited
- Blood draw under a warrant or implied consent. Texas labs typically test for THC and its metabolites.
Under Texas Transportation Code §724.011, operating a vehicle on a public road constitutes implied consent to a breath or blood specimen if arrested for DWI. Refusal triggers an automatic 180-day license suspension for a first refusal (longer for repeat refusals), and officers can — and routinely do — obtain a search warrant for a forced blood draw [7]. The U.S. Supreme Court in Missouri v. McNeely (2013) required a warrant absent exigent circumstances for blood draws, and Birchfield v. North Dakota (2016) restricted warrantless blood tests as a condition of implied-consent laws [8]. Strong evidence
Penalties
Penalties under §49.04 do not distinguish between alcohol and cannabis:
- First offense: Class B misdemeanor — up to 180 days jail (minimum 72 hours), up to $2,000 fine, license suspension up to 1 year [1].
- Second offense: Class A misdemeanor — up to 1 year jail, up to $4,000 fine.
- Third offense: Third-degree felony — 2 to 10 years prison, up to $10,000 fine.
- DWI with child passenger (under 15): State jail felony under §49.045.
- Intoxication assault (§49.07) or intoxication manslaughter (§49.08): second- and third-degree felonies respectively.
A "superfine" added by HB 2048 (2019) imposes an additional $3,000–$6,000 civil penalty for DWI convictions on top of criminal fines [9]. Surcharges previously assessed under the Driver Responsibility Program were repealed in 2019 [9].
Medical cannabis and the Compassionate Use Program
Texas's Compassionate Use Program (TCUP) allows low-THC cannabis (up to 1% THC by weight as of HB 1535, 2021) for qualifying patients [10]. TCUP enrollment is not a defense to DWI. Section 49.10 of the Penal Code explicitly states that the fact a defendant is or has been entitled to use a substance is not a defense to prosecution under Chapter 49 [2]. A registered patient driving impaired by their prescribed product can still be convicted. Strong evidence
Hemp, delta-8, and lab complications
Federal and Texas law (HB 1325, 2019) legalized hemp containing ≤0.3% delta-9 THC [11]. Standard forensic blood tests detect delta-9 THC but do not always distinguish its source. A driver who legally consumed a hemp-derived delta-8 or delta-9 product could test positive and face DWI prosecution if impairment is shown. The legality of the product does not negate the intoxication element — see §49.10 [2]. Delta-8's legal status in Texas itself remains in active litigation as of mid-2024 [12]. Disputed
Practical notes
- There is no safe "wait time" published by the State of Texas after consuming cannabis. Peer-reviewed reviews suggest acute impairment from smoked cannabis typically lasts 3–10 hours depending on dose and route, with edibles lasting longer [4]. Weak / limited
- Odor of marijuana alone has historically supported probable cause to search a vehicle in Texas, though post-hemp legalization some courts have questioned this; the rule is unsettled [13]. Disputed
- Refusing SFSTs is not itself a crime, but refusal can be used as evidence and does not prevent arrest.
- An Administrative License Revocation (ALR) hearing is separate from the criminal case and must be requested within 15 days of arrest.
For related background see Cannabis Possession Laws in Texas and THC Blood Testing and Driving.
Sources
- Government Texas Penal Code §49.04 — Driving While Intoxicated.
- Government Texas Penal Code §49.01 (Definitions) and §49.10 (No Defense).
- Government National Conference of State Legislatures, "Drugged Driving | Marijuana-Impaired Driving," updated 2023.
- Peer-reviewed Huestis MA. "Human Cannabinoid Pharmacokinetics." Chemistry & Biodiversity, 2007;4(8):1770-1804.
- Peer-reviewed Downey LA, et al. "The effects of cannabis and alcohol on simulated driving: Influences of dose and experience." Accident Analysis & Prevention, 2013;50:879-886.
- Peer-reviewed Porath-Waller AJ, Beirness DJ. "An examination of the validity of the Standardized Field Sobriety Test in detecting drug impairment using data from the Drug Evaluation and Classification Program." Traffic Injury Prevention, 2014;15(2):125-131.
- Government Texas Transportation Code Chapter 724 — Implied Consent.
- Government Missouri v. McNeely, 569 U.S. 141 (2013); Birchfield v. North Dakota, 579 U.S. 438 (2016).
- Government Texas HB 2048 (86th Legislature, 2019) — Repeal of Driver Responsibility Program; DWI superfine.
- Government Texas Department of Public Safety, Compassionate Use Program overview.
- Government Texas HB 1325 (86th Legislature, 2019) — Hemp production and consumable hemp products.
- Reported Texas Tribune, "Texas Supreme Court allows ban on delta-8 THC products to be challenged," 2023.
- Reported Texas Monthly, "Now That Hemp Is Legal, Can Texas Cops Still Search Your Car for Pot?" 2019.
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