Criminal Defense AttorneyDUIPrince George's CountyThe Law Offices of Haskell & DyerLawful Use, Unlawful Driving: Maryland Marijuana DUI Defense in Prince George’s County

Marijuana DUI cases have grown substantially in volume across Prince George’s County since legalization. The pattern is recognizable: a driver consumes marijuana legally at home or in a permitted setting, drives later, and gets stopped for an unrelated traffic offense. The officer detects an odor, observes red eyes or slow reactions, and the case proceeds as a marijuana DUI investigation. The driver’s lawful consumption does not protect against a DUI charge if the State can prove impairment.

This article walks through how marijuana DUI cases proceed in Prince George’s County and where the defense usually finds traction. For the broader DUI and traffic framework, see our complete Prince George’s County DUI and traffic defense guide.

The Statutory Framework

Maryland prohibits driving while impaired by any drug, combination of drugs, or alcohol and a drug under § 21-902(c) and (d). The drug DUI framework reaches both prescription medications and controlled or formerly controlled substances, including marijuana. Adult recreational use was legalized through the constitutional amendment approved in 2022 and the implementing legislation effective in 2023, but the DUI statute was not amended to create a per se threshold for THC.

The absence of a per se threshold means the State must prove impairment under a totality of the circumstances analysis. The evidence typically includes the driving conduct that prompted the stop, the officer’s observations of the driver’s appearance and behavior, the SFST performance, any admissions of consumption, the odor of marijuana, and (in some cases) blood test results showing THC presence.

The penalties on conviction are the same as for alcohol DUI under § 21-902. A first offense reaches up to one year of incarceration and a $1,000 fine. A first offense impaired conviction (§ 21-902(b) or (c)) reaches up to two months and $500. The MVA administrative consequences also follow the same framework, with license suspension for breath/blood test failure or refusal.

The Detection Versus Impairment Problem

The central scientific issue in marijuana DUI cases is the difference between THC detection and current impairment. THC’s primary psychoactive effects on the central nervous system typically last two to four hours after smoking and somewhat longer after edible consumption, with residual effects that can extend several hours more. Detection of THC in blood, however, can extend to days or weeks after consumption, particularly for chronic users whose body fat stores release THC slowly over time.

The implication is that a blood test showing THC presence does not establish current impairment. A daily medical marijuana patient who last consumed eighteen hours before a stop may still test positive for THC well above any conceivable impairment threshold. A weekly recreational consumer may test positive a week or more after consumption. The State’s expert witnesses sometimes conflate the detection of THC with the existence of impairment, and defense counsel develops the distinction at trial through cross-examination and, in serious cases, through defense expert testimony.

The peer reviewed scientific literature on marijuana impairment is substantial and increasingly consistent on this point. The National Highway Traffic Safety Administration has acknowledged that no reliable per se threshold exists for THC, and several states with legalized markets have struggled with the same evidentiary issues. Defense counsel familiar with the literature can use it to substantial effect at trial.

Drug Recognition Evaluations

Some Maryland law enforcement agencies maintain trained Drug Recognition Experts (DREs) who conduct multi-step evaluations to identify and classify drug impairment. The DRE protocol involves a 12 step examination including pupil measurement, vital sign assessment, balance and coordination tests, dark room examinations of pupil reactions, and other components. The DRE is supposed to identify the category of substance involved (CNS depressant, CNS stimulant, hallucinogen, dissociative anesthetic, narcotic analgesic, inhalant, or cannabis) based on the combination of observed indicators.

The DRE methodology has substantial reliability concerns. Independent peer reviewed studies have found accuracy rates that fall well short of the certainty often suggested at trial. The 12 step protocol relies heavily on subjective observations that are prone to confirmation bias once the DRE has formed an initial impression. The classification scheme has overlap among categories that can produce category errors. Maryland courts have admitted DRE testimony, but defense counsel can develop the limitations through cross-examination and, in some cases, through defense expert testimony.

The SFST Problem with Marijuana

The standardized field sobriety test battery was developed and validated for alcohol impairment. The horizontal gaze nystagmus, the walk and turn, and the one leg stand were designed and tested to identify alcohol related impairment, and the validation studies focused exclusively on alcohol. The application of the same battery to marijuana impairment is not supported by equivalent validation work.

NHTSA has acknowledged this limitation in its training materials, but the practical effect at trial is that the State often presents SFST results as evidence of marijuana impairment when the underlying validation does not support that use. Defense counsel develops the limitation carefully, both to limit the weight given to SFST evidence and (in some cases) to support defense expert testimony on the inappropriateness of the application.

Defense Strategy

Effective defense in marijuana DUI cases follows several patterns. First, focus on the impairment versus detection distinction. The State must prove actual impairment, not merely consumption history. Second, attack the SFST application; the battery was not designed for marijuana and its application produces unreliable results. Third, evaluate any DRE testimony for methodological and procedural concerns. Fourth, develop alternative explanations for the observed indicators (red eyes from allergies or tiredness, slow speech from individual personality, slow reactions from age or other conditions, etc.). Fifth, consider expert testimony in cases where the State’s evidence rests heavily on DRE or SFST findings.

Related Reading

• From the Capital Beltway to the Hyattsville Bench: The Complete PG County DUI and Traffic Defense Guide
• Capital Beltway DUI Defense
• MVA Administrative Hearing Defense

References