Marijuana DUI in Rhode Island After Legalization: No Per Se THC Limit, DRE Testimony, and Saliva Tests

A marijuana DUI in Rhode Island is charged under the same statute as an alcohol DUI, R.I. Gen. Laws § 31-27-2, and legalization did not change that. Adult-use cannabis became legal on May 25, 2022 under the Rhode Island Cannabis Act, but the Act says it does not permit anyone to operate a motor vehicle while under the influence of cannabis, and it gives no defense to a DUI charge. What legalization changed is the evidence.

Rhode Island does not have a per se THC limit. That one fact drives every marijuana DUI case that lands on my desk at 127 Dorrance Street. Without a nanogram threshold, the prosecutor has to prove you were actually impaired when you drove. That proof usually comes from an officer's observations, a Drug Recognition Expert (DRE) evaluation, and a blood or urine result that by itself says very little about impairment. Those are the three things I attack.

Legal to Use, Still Illegal to Drive Impaired

Section 21-28.11-22 of the Cannabis Act lets a person 21 or older possess and use up to one ounce. Section 21-28.11-29 draws the line at the driver's seat: the chapter does not permit driving under the influence of cannabis. It then adds a sentence I quote to prosecutors regularly. A person shall not be considered under the influence solely for having cannabis metabolites in his or her system. And under § 31-27-2(b)(1), being legally entitled to use a drug is not a defense.

For a first offense, § 31-27-2(d)(1)(iii) puts a driver under the influence of a drug in the same tier as a 0.15 alcohol reading: a $500 fine, 20 to 60 hours of community restitution, up to one year in jail, a license suspension of 3 to 18 months, a DWI course or treatment, a $500 highway assessment and an $86 fee. The Rhode Island drug DUI page at riduilaws.com lays out every tier.

Why No Per Se THC Limit Matters

With alcohol, § 31-27-2(b)(1) says a 0.08 reading is enough. With marijuana there is no line, so the state has to prove you were under the influence to a degree that rendered you incapable of safely operating the vehicle.

Blood THC does not track impairment the way blood alcohol does. Active THC spikes within minutes of smoking and drops fast, often while the person still feels the effects, and a daily user can carry measurable THC a day or more after last use with no impairment. The carboxy-THC metabolite that urine tests detect is inactive and can sit in the body for weeks. That is why a urine result tells the jury nothing about the drive.

At trial the state's toxicologist will say THC was present and that THC can impair. I cross-examine on what the number cannot say: when, how much, whether the driver was tolerant, and whether any accepted threshold ties that number to unsafe driving. None exists.

The Drug Recognition Expert Protocol

Because there is no number, § 31-27-2(b)(1) allows a conviction based on the testimony of a drug recognition expert certified through training approved by the Rhode Island Department of Transportation Office on Highway Safety. A DRE is a police officer, not a doctor. The evaluation has 12 steps, almost always done at the station after the arrest:

1. Breath alcohol test.
2. Interview of the arresting officer.
3. Preliminary examination and first pulse.
4. Eye examinations: horizontal and vertical gaze nystagmus, lack of convergence.
5. Divided attention tests: Romberg balance, walk and turn, one leg stand, finger to nose.
6. Blood pressure, temperature and second pulse.
7. Dark room pupil measurements and nasal and oral cavity check.
8. Muscle tone.
9. Injection site check and third pulse.
10. Statements of the subject.
11. Opinion of the evaluator, naming a drug category.
12. Toxicology sample.

For cannabis, the matrix expects no nystagmus, lack of convergence, dilated pupils, a faster pulse and higher blood pressure.

Where I Cross-Examine a DRE

Timing. The 12 steps come after the arrest, so the DRE opinion cannot supply probable cause for an arrest that already happened. I make the arresting officer justify the arrest on the roadside facts alone.

Innocent explanations. Dilated pupils, a faster pulse and higher blood pressure are also what fear looks like at 1 a.m. in a police station. Lack of convergence shows up in plenty of sober people. I ask the DRE whether each indicator has any cause other than cannabis. The answer is always yes.

Corroboration. The DRE program teaches that toxicology should confirm the opinion. In a cannabis case it confirms presence only, so the opinion stands on observations alone.

Validation. The standardized field sobriety tests given before the DRE evaluation were validated for alcohol, not cannabis.

The Odor of Marijuana After Legalization

The smell of marijuana still starts many of these cases. The Rhode Island Supreme Court addressed part of the problem in State v. Li and State v. Kuang, Nos. 2021-153-C.A. and 2021-154-C.A. (R.I. July 27, 2023). An officer prolonged a seat belt stop after noticing a slight odor of fresh marijuana, and a K-9 sniff followed. The Supreme Court held that the odor of raw or fresh marijuana, standing alone, remains a factor in the totality of the circumstances for reasonable suspicion, because possessing more than the legal amount is still a crime. The Court limited its holding to fresh marijuana and did not reach burnt odor. One justice dissented.

That leaves the question that matters in a DUI case open: whether burnt marijuana odor, by itself, supports reasonable suspicion of impaired driving or probable cause to arrest. I argue it does not. A burnt odor says someone smoked at some point and nothing about when, who, or whether the driver is impaired now. An arrest needs facts about the driver: the driving, speech, coordination, roadside tests, admissions.

Roadside Saliva Tests in Rhode Island

Both § 31-27-2(c) and § 31-27-2.1(a) now list breath, blood, saliva and urine as fluids subject to chemical testing. That does not mean a roadside oral fluid swab decides your case.

Under § 31-27-2(c), a chemical test result is admissible only if the state proves your consent, a true copy of a fluid result mailed within 30 days, a test performed by methods and equipment approved by the Department of Health, and notice of your right to an additional test. A curbside swab is a screening tool that measures presence, not impairment. I follow the marijuana breath test technology for the same reason.

Refusing the Chemical Test in a Marijuana Case

Breath machines measure alcohol, not THC, so in a marijuana DUI the officer asks for blood or urine, and the implied consent law, § 31-27-2.1, applies. Refusal is a separate charge heard at the Rhode Island Traffic Tribunal, 670 New London Avenue in Cranston, on its own track from the criminal case.

A first refusal carries a suspension of 6 months to 1 year, a fine of $200 to $500, 10 to 60 hours of community restitution, a $500 highway assessment and a $200 Department of Health assessment. Refusing a blood test is always a civil offense, even on a repeat refusal within 10 years. Refusing breath or urine a second time within 10 years is a misdemeanor with up to 6 months in jail. My office handles the Tribunal side as part of any chemical test refusal defense. Under § 31-27-2(c)(1), your refusal cannot be used against you at the criminal trial unless you choose to testify.

How I Handle These Cases

First, I get the video. Without a number, cruiser and body camera footage is the closest thing to an objective witness.

Second, I pull the stop apart: why the car was stopped, what the officer smelled and when, and the moment a traffic stop became a DUI investigation. If odor is the only bridge to the arrest, I file a motion to suppress.

Third, I get the DRE worksheet, certification and rolling log and compare the recorded indicators to the cannabis matrix, then I deal with the lab: which fluid, active THC or metabolite, and whether the § 31-27-2(c) conditions were met.

Fourth, I prepare every case as if it will be tried. My page on fighting a DUI charge in Rhode Island walks through each stage.

Frequently Asked Questions

Is there a legal THC limit for driving in Rhode Island?

No. Rhode Island has no per se THC limit in § 31-27-2. The state must prove you were under the influence of cannabis to a degree that made you incapable of driving safely. A THC number alone does not establish that.

Can I be charged with DUI if I have a medical marijuana card?

Yes. Section 31-27-2(b)(1) says being legally entitled to use a drug is not a defense to DUI, and the Cannabis Act says the same. A card can matter on search and possession issues, but not on whether you were impaired while driving.

Does the smell of marijuana give police the right to search my car?

The Rhode Island Supreme Court held in State v. Li in 2023 that the odor of fresh marijuana remains a factor in reasonable suspicion because possessing over one ounce is still a crime. The Court did not decide the burnt odor question.

What happens if I refuse a blood or urine test in a marijuana DUI?

You face a separate refusal charge under § 31-27-2.1 at the Traffic Tribunal, with a 6 month to 1 year suspension, fines and assessments for a first offense. Refusing blood is always civil. A second refusal of breath or urine within 10 years can be a misdemeanor.

Are police in Rhode Island using roadside saliva tests?

The statutes now list saliva as a fluid subject to chemical testing, but any result must meet the admissibility conditions in § 31-27-2(c), including Department of Health approved methods and equipment. A roadside swab is a screening tool that measures presence, not impairment.

Can a DRE officer alone convict me of a marijuana DUI?

The statute allows it, so yes in theory. In practice a DRE opinion rests on indicators with many innocent causes, a protocol performed after the arrest, and toxicology that only confirms presence. Each is a point I cross-examine.

Charged With a Marijuana DUI? Call Me

If you have been arrested for a marijuana DUI anywhere in Rhode Island, call me at 401-573-2265. I answer 24/7 and the consultation is free. My offices are at 127 Dorrance Street in Providence, next to the Garrahy Judicial Complex, and at 970 Main Street, Suite 2, in West Warwick. As a RI DUI lawyer for more than 20 years, I will tell you honestly where your case is strong and where it is not.

This article is general information about Rhode Island law, not legal advice for your specific case.