Tennessee Cannabis DUI — Impairment-Based, No Per-Se THC Limit

Last verified: May 2026

The DUI Statute

Tennessee’s DUI statute at T.C.A. § 55-10-401 sets multiple alternative theories of culpability. For cannabis cases, the operative theory is impairment "by any intoxicant, marijuana, controlled substance ... that impairs the driver’s ability to safely operate a motor vehicle by depriving the driver of the clearness of mind and control of oneself that the driver would otherwise possess." The 0.08% BAC per-se theory applicable to alcohol is unavailable for cannabis — Tennessee has not adopted a per-se THC blood limit comparable to the 5 ng/mL threshold of CO, IL, MT, NV, OH, PA, or WA.

Penalties Under T.C.A. § 55-10-403

Tennessee DUI penalties scale by prior convictions:

• 1st DUI: 48 hours–11 months 29 days jail; $350–$1,500 fine; 1-year license revocation.
• 2nd DUI (within 10 years): 45 days–11 mo 29 days; $600–$3,500; 2-year revocation.
• 3rd DUI: 120 days–11 mo 29 days; $1,100–$10,000; 6-year revocation.
• 4th+ DUI: Class E felony; 150+ consecutive days, day-for-day; $3,000–$15,000; 8-year revocation.
• DUI with child under 18 in the vehicle: +30 days mandatory; +$1,000 mandatory.

A $100 alcohol-and-drug-addiction-treatment fee is assessed for each conviction. Court costs and statutory fees typically add another $1,000–$2,500 to total exposure. Insurance consequences (SR-22 filing for 3 years; non-renewal by carrier; rate increases of 50–200%) typically exceed direct fine costs.

Implied Consent — T.C.A. § 55-10-406

Operating a vehicle on Tennessee roads is statutory consent to chemical testing (blood, breath, or both) when an officer has reasonable grounds. Refusal results in automatic license revocation:

• 1st refusal: 1-year revocation
• 2nd refusal: 2-year revocation
• Refusal in DUI involving injury: 2-year revocation
• Refusal in DUI involving death: 5-year revocation

Refusal can also be introduced as evidence at trial as consciousness of guilt — an additional reason a defense lawyer may advise that test refusal is not always the optimal litigation posture in cannabis-DUI cases (where the absence of a per-se threshold means a prosecution must prove impairment regardless of test results).

Drug Recognition Expert (DRE) Protocol

Tennessee Highway Patrol and most municipal departments train DRE officers under the standard 12-step protocol developed by the International Association of Chiefs of Police. The protocol is designed to identify drug categories (CNS depressants, CNS stimulants, hallucinogens, dissociative anesthetics, narcotic analgesics, inhalants, cannabis) through:

• Breath-alcohol test (rule out alcohol).
• Pulse / blood-pressure / temperature.
• Eye examination (HGN, VGN, lack of convergence, pupil size).
• Divided-attention tests (Romberg balance, walk-and-turn, one-leg stand, finger-to-nose).
• Vital-signs second check.
• Dark-room examination of pupil size in three light conditions.
• Muscle-tone examination.
• Injection-site examination.
• Subject statements and interview.
• Officer’s opinion on category.
• Toxicology corroboration (urine sample).

DRE evidence is admissible in Tennessee courts. Defense attorneys regularly challenge DRE qualifications, the reliability of the 12-step protocol generally (the National Highway Traffic Safety Administration training is the standard), and the specific officer’s adherence to protocol on the night in question. Cross-examination on field-condition variables (lighting, weather, clothing, the subject’s baseline physical condition) is routine.

Ignition Interlock and Restricted Licenses

Effective January 2016, an ignition interlock device is mandatory for restricted-license holders if any of the following apply: BAC ≥0.08%; DUI with both alcohol and drugs; child under 18 in vehicle at time of offense; DUI involving an accident; implied-consent violation with prior; prior DUI within 10 years; driver request; or court discretion. The device must be installed at the driver’s expense (the Ignition Interlock Fund under T.C.A. § 55-10-419 provides indigency assistance).

The Hemp-Confound

The single most distinctive feature of Tennessee cannabis DUI law is its interaction with the legal hemp market. Because Tennessee does not have a per-se THC limit, hemp-derived delta-9 THC, delta-8 THC, and THCA-converted-to-THC consumers can be charged with DUI based on impairment evidence alone — and Tennessee DRE protocols do not distinguish between legal hemp-derived intoxication and prohibited marijuana intoxication.

Standard urine drug tests detect THC metabolites (THC-COOH) but cannot identify the source of the THC. Hemp-derived delta-9, delta-8, and THCA all metabolize through pathways that produce the same THC-COOH metabolite as marijuana-derived delta-9. The Tennessee Traffic Safety Resource Service has cautioned that one practical effect of the hemp-intoxicant market has been "barely regulated recreational cannabis" and corresponding rises in drugged-driving cases.

Defense attorneys raise the hemp-distinction in DUI litigation:

• Where probable cause for the stop or arrest depends on alleged "smell of marijuana," defense argues that legal hemp products produce indistinguishable odor.
• Where toxicology shows THC metabolites, defense may introduce evidence the defendant was a regular consumer of legal hemp products at retailers operating under TDA legacy licenses.
• Where DRE evaluation supports cannabis-category impairment, defense may argue impairment is from legal substances and challenge the inference of voluntary intoxication "by any intoxicant" under the impairment standard.

Tennessee courts have not yet definitively ruled on hemp-DUI defense theory. Some county-level acquittals have rested on hemp-distinction defenses; the Tennessee Supreme Court has not issued a controlling opinion as of May 2026.

Practical DUI Considerations

• Cannabis impairment timing: peak impairment from inhalation is 30–60 min post-consumption; from edibles, 1–3 hr. THC-COOH metabolites can persist in urine for 30+ days for chronic users without correlation to current impairment.
• Combination cases: Tennessee prosecutors regularly add controlled-substance possession charges (T.C.A. § 39-17-418) to DUI charges when cannabis is found in the vehicle, exposing the defendant to dual-track misdemeanor exposure.
• Open-container provisions: T.C.A. § 55-10-416 prohibits "open-container" possession of any alcoholic beverage in the passenger area; Tennessee does not have a parallel cannabis-open-container statute, but THP and municipal officers regularly cite passenger-area cannabis possession.
• CDL drivers: 49 C.F.R. Part 382 imposes federal zero-tolerance on marijuana metabolites for commercial drivers; a positive screen triggers FMCSA Drug & Alcohol Clearinghouse reporting and bars safety-sensitive functions pending return-to-duty completion. See FedEx / DOT / FMCSA page.

Related on this site: Casual Exchange & Distribution, Tennessee Concentrate, Tennessee Cultivation.