Maryland legalized recreational cannabis in July 2023, but that didn’t change one thing: driving under its influence is still a criminal offense. What did change is how confusing the legal landscape became. Unlike alcohol, there’s no number the state can point to and say “you’re over the limit.” Here’s how a drug DUI actually gets built and challenged in Maryland.
No Per Se Limit: Why That Actually Makes Cases More Complicated, Not Less
Alcohol DUI in Maryland works off a bright line: 0.08% BAC, and the state doesn’t need to prove you were actually intoxicated, just that you were over the number. Drug DUI doesn’t have that shortcut. Maryland has no established “per se” THC limit the way it does for alcohol. Under Transportation Article §21-902(c) and (d), the state has to prove actual impairment, meaning you couldn’t drive safely, not just that a substance was present in your system.
That might sound like it favors drivers, but in practice it means prosecutors lean harder on subjective evidence: officer observations, field sobriety test performance, and Drug Recognition Expert (DRE) evaluations. Where an alcohol case can hinge on a single number, a drug case often comes down to how convincingly the state can describe your behavior and how well your attorney can challenge that description.
What a DRE Evaluation Actually Involves
A Drug Recognition Expert is a specially trained officer who conducts a standardized 12-step evaluation when a non-DRE officer suspects drug impairment, typically because a driver’s behavior doesn’t match their alcohol test result. According to Dr. Timothy Kerns, director of the Maryland MVA’s Highway Safety Office, DRE officers are trained to identify seven different drug classifications, covering both stimulants and depressants, and are called in specifically when an alcohol test comes back negative but impairment still seems evident.
Maryland has expanded this program significantly since legalization. As of late 2025, 18 of Maryland’s 24 jurisdictions had at least one DRE on staff, with 59 DRE instructors statewide.
How Accurate Is DRE Testimony, Really?
This is the part most explanations skip entirely, and it matters more than people realize. A peer-reviewed study published in Traffic Injury Prevention analyzed 4,931 Maryland DRE evaluations from 2017 to 2021, comparing DRE officer opinions against actual blood test results. The findings:
- Overall agreement between DRE opinion and blood test results: 84.2%
- Accuracy when zero or one drug was involved: 91.8%
- Accuracy when two or more drugs were involved: 80.5%
In plain terms, DRE evaluations are reasonably reliable in straightforward cases but noticeably less so in more complex ones, exactly the cases where the stakes tend to be higher. That gap is a legitimate basis for challenging DRE testimony in court, not just a talking point.
This isn’t hypothetical. In one Maryland case, the Circuit Court for Carroll County excluded DRE evidence entirely, holding that DRE identification and classification “is not generally accepted as valid and reliable in the relevant scientific community.” The court’s opinion pointed to specific weaknesses: questions about the standardized drug matrix, how nystagmus is diagnosed, whether an officer is qualified to diagnose what are effectively medical conditions, and a lack of peer-reviewed research validating the DRE protocol itself. This is exactly the kind of precedent that matters when an attorney is deciding whether to challenge DRE testimony rather than simply negotiate around it.
The Detection Window Problem
THC behaves nothing like alcohol in the body. Alcohol metabolizes at a predictable rate, which is why a BAC number can reliably indicate recent consumption. THC is different. It can remain detectable in blood or urine for days, sometimes weeks, after use, long after any actual impairment has worn off. A positive drug test doesn’t necessarily mean you were impaired at the time you were driving, and this gap between “detected” and “impaired” is one of the more consistently useful angles in defending a marijuana DUI case.
What’s Actually Happening Since Legalization
The data tells a more complicated story than either side of the legalization debate usually admits. According to the 2025 Maryland Cannabis Use Biannual Study, self-reported driving under the influence of cannabis roughly doubled in the months immediately following legalization, from about 18% in 2022 to 39% in 2023. At the same time, cannabis positive DRE evaluations made up about 25% of all DRE evaluations in 2023, and statewide drug-impaired driving arrests have actually dropped more than 70% over the past seven years, a figure the study doesn’t break out by substance. Law enforcement officials, including a First Sergeant with the Maryland State Police Chemical Test for Alcohol Unit, have publicly noted that the number of drivers charged with cannabis-related DUI hasn’t changed significantly since legalization, despite the jump in self-reported use.
Read together, this suggests enforcement hasn’t necessarily caught up with behavior change, which cuts both ways: it doesn’t mean cannabis-impaired driving isn’t happening, but it does mean the cases that do get charged are being built carefully, often specifically through DRE evaluation rather than routine traffic stops.
Penalties Are the Same as Alcohol DUI, With One Important Difference
A drug DUI conviction under §21-902(c) carries the same penalty range as a standard alcohol DUI: up to a year in jail and a fine on a first offense, with harsher exposure for repeat offenses, plus 12 points added to your Maryland driving record under the same point system that applies to alcohol DUI convictions. Combined alcohol-and-drug impairment is treated even more seriously; it’s charged and penalized in line with standard DUI rather than the lesser DWI tier, reflecting that combined impairment is generally considered more dangerous than either substance alone. For the specific numbers involved, see our guide to Maryland DUI penalties.
Drivers under 21 face zero tolerance: any detectable amount of cannabis is a violation, regardless of behavioral impairment, separate from the standard adult framework described here.
Worth Remembering: Legal in Maryland Doesn’t Mean Legal Everywhere
Cannabis purchased legally in Maryland remains illegal to transport across state lines, even briefly, into Delaware, Virginia, Pennsylvania, DC, or West Virginia, since it’s still federally illegal. That’s a separate legal exposure from a DUI charge, but it’s a detail that catches people off guard, particularly in the DC-Maryland-Virginia area where crossing a state line during an ordinary day is routine.
Can a Lawyer Actually Help With a Drug DUI Case?
Because these cases rely so heavily on subjective evaluation rather than a hard number, the quality of the challenge matters more here than in a straightforward alcohol case. An attorney can examine whether the DRE followed the standardized protocol correctly, challenge the reliability of the evaluation given the accuracy gaps described above, and raise the detection-window problem where it applies. If your case involved a DRE evaluation, or you’re unsure whether the state can actually prove impairment rather than just presence, our Maryland DUI defense attorneys can walk you through what the evidence in your specific case actually shows.
For official information on Maryland’s DRE program, the Maryland DRE program’s official site is a public resource. For general guidance on the criminal process after any DUI arrest, see our guide to the DUI legal process in Maryland.
Frequently Asked Questions
Can I get a DUI in Maryland for driving after using legal, prescribed medication? Yes, potentially. Maryland’s drug DUI law covers impairment from any substance, including legally prescribed medication, if it actually impairs your ability to drive safely. Legal access to a substance isn’t a defense to impairment.
How does a DRE evaluation differ from a regular field sobriety test? A DRE evaluation is a longer, more structured 12-step process specifically designed to identify which category of drug may be causing impairment, conducted by an officer with specialized training, typically after a standard alcohol test comes back negative or doesn’t match observed behavior.
Can DRE testimony be challenged in court? Yes. Maryland courts have excluded DRE evidence in specific cases where the reliability of the underlying methodology was successfully challenged. Whether that’s a viable strategy depends heavily on the specifics of your case and evaluation.
Does a positive drug test prove I was impaired while driving? Not necessarily. Because substances like THC can remain detectable long after impairment has worn off, a positive test shows presence, not necessarily impairment at the time of driving. This distinction is often central to a drug DUI defense.
Is a marijuana DUI treated differently than an alcohol DUI in terms of punishment? The penalty structure is largely the same, though a case involving combined alcohol and drug impairment is treated more seriously and charged in line with standard DUI rather than the lesser DWI offense.