The Legal Standard for Drug Impairment
Under Transportation Article §21-902(c), it is unlawful to drive while so far impaired by any drug, combination of drugs, or combination of drugs and alcohol that the person cannot drive safely. This standard differs from the alcohol DWI standard — drug impairment requires not just some impairment, but impairment sufficient to render the driver unable to drive safely.
Under Transportation Article §21-902(d), driving while impaired by a controlled dangerous substance (CDS) as defined in Criminal Law Article §5-101 — when the driver is not legally entitled to use the substance — carries its own penalties.
Under §21-902(c)(1)(iv), lawful use of a drug is a defense to a drug impairment charge — but only if the defendant was unaware that the drug or combination would make them incapable of safely driving a vehicle. If you were prescribed a medication that impaired your driving, an experienced attorney can evaluate whether this statutory defense applies to your specific circumstances and medication.
Cannabis and Driving in Maryland
The legalization of recreational cannabis in Maryland in 2023 did not create a right to drive while impaired by cannabis. Maryland law does not establish a specific THC blood level equivalent to the 0.08% BAC threshold for alcohol — there is no "legal limit" for cannabis impairment. This means drug impairment cases involving cannabis rely entirely on observed behavioral evidence and Drug Recognition Expert (DRE) evaluation rather than a chemical threshold.
Maryland law also prohibits smoking or consuming cannabis in the passenger area of a motor vehicle on a highway under §21-903(c), regardless of impairment.
Drug Recognition Expert (DRE) Evaluations
In cases involving suspected drug impairment, officers may request a Drug Recognition Expert evaluation. DRE officers follow a 12-step protocol to evaluate whether drug impairment is present and to identify the drug category allegedly causing impairment. The DRE protocol includes:
- Breath alcohol test to rule out or quantify alcohol impairment
- Interview of the arresting officer
- Preliminary examination including pulse rate and eye checks
- Eye examinations (HGN, vertical nystagmus, lack of convergence)
- Divided attention tests (modified Romberg, Walk-and-Turn, One-Leg Stand, finger-to-nose)
- Vital signs examination (pulse, blood pressure, body temperature)
- Dark room examination (pupil size under three lighting conditions)
- Muscle tone examination
- Injection sites examination
- Statements and other observations
- DRE officer's opinion of impairment and drug category
- Toxicological examination (blood or urine)
Challenging Drug Impairment Evidence
Drug DUI cases often present strong defense opportunities because:
- No standardized chemical threshold — Without a BAC-equivalent number, the State must prove functional impairment through behavioral evidence alone, which is more subjective and contestable.
- Presence does not equal impairment — Many substances, including cannabis metabolites, remain detectable in blood and urine long after any impairing effect has passed. A positive drug test does not prove impairment at the time of driving.
- DRE methodology challenges — The DRE protocol's scientific validity has been subject to ongoing challenge in courts. DRE officers' opinions are not universally accepted as reliable scientific evidence.
- Prescription drug defense — If you were taking a legally prescribed medication and were unaware it would affect your driving ability, this statutory defense may apply.
- Alternative explanations for observations — Medical conditions, fatigue, and environmental factors can produce the same behavioral signs officers attribute to drug impairment.
First Offense Penalties — TR §21-902(c) and (d)
| Charge | Statute | Standard | Max Jail | Max Fine |
|---|---|---|---|---|
| Driving While Impaired by Drug(s) | §21-902(c)(1) | So impaired by drug(s) or drugs+alcohol that driver cannot drive safely | 2 months | $500 |
| Drug Impairment with Minor in Vehicle | §21-902(c)(2) | Same standard; minor being transported | 1 year | $1,200 |
| Driving While Impaired by CDS | §21-902(d)(1) | Impaired by CDS while not legally entitled to use it | 1 year | $1,200 |
| CDS Impairment with Minor in Vehicle | §21-902(d)(2) | Same standard; minor being transported | 2 years | $2,000 |