The Core Legal Distinction
Under Maryland Transportation Article §21-902, both DUI and DWI prohibit operating a vehicle while impaired by alcohol — but the degree of impairment required differs significantly between the two charges.
DUI (Driving Under the Influence) under §21-902(a) requires that alcohol substantially impaired the person's normal coordination. It is the more serious charge.
DWI (Driving While Impaired) under §21-902(b) requires that alcohol impaired the person's normal coordination to some extent. It carries lower penalties but is still a criminal charge with real consequences.
Critically, neither charge is defined by a specific blood alcohol content number. The Maryland Criminal Pattern Jury Instructions (MPJI-Cr 4:10) confirm that both charges can be proven through observed behavior alone — without any BAC reading.
The jury instruction for DUI states that the charge requires alcohol to have substantially impaired the person's normal coordination. The instruction for DWI states only that alcohol impaired coordination to some extent. Neither instruction references a specific BAC threshold as an element of the offense. A BAC reading affects what inferences a jury may draw — it does not define the charge.
How BAC Readings Affect Each Charge
While BAC is not an element of either offense, it does affect the evidentiary inferences available under MPJI-Cr 4:10.4:
| BAC Reading | DUI Inference | DWI Inference |
|---|---|---|
| 0.08% or higher | Jury may (but is not required to) find DUI or DWI from this amount alone | Jury may (but is not required to) find DWI from this amount alone |
| 0.07% | Jury may consider but cannot find DUI based solely on this level | Jury may (but is not required to) find DWI based solely on this level |
| Above 0.05%, below 0.07% | Jury may consider but cannot find DUI or DWI based solely on this level | Jury may consider but cannot find DWI based solely on this level |
| 0.05% or less | Presumption of sobriety — State must overcome this presumption beyond a reasonable doubt with other evidence | |
Penalties Compared
| Charge | Statute | Max Jail | Max Fine | MVA Points | License Suspension |
|---|---|---|---|---|---|
| DUI | §21-902(a)(1) | 1 year | $1,200 | 12 points | Up to 6 months |
| DWI | §21-902(b)(1) | 2 months | $500 | 8 points | Up to 6 months |
Despite the lower penalties, a DWI conviction is still a criminal record entry that can affect employment, professional licensing, housing applications, and future charging decisions. It is not simply a traffic ticket.
How Officers Charge DWI Without a BAC Reading
Because DWI is defined by observed impairment rather than a BAC number, officers regularly charge DWI based entirely on behavioral observations at the scene:
- Erratic driving patterns observed prior to the stop
- Slurred speech during the traffic stop interaction
- Bloodshot or watery eyes
- Odor of alcohol on breath or in the vehicle
- Difficulty locating license, registration, or insurance documents
- Unsteady gait or balance issues outside the vehicle
- Performance on Standardized Field Sobriety Tests
A DWI charge based solely on these observations — with no BAC reading — is still a criminal charge that must be defended aggressively. The absence of a BAC result does not make the case go away; it means the State's entire case rests on officer testimony and field sobriety performance.
Defense Strategies
Whether you are charged with DUI or DWI, the defense analysis is similar — but the absence of a BAC reading in a DWI case opens additional lines of attack:
- Challenging the traffic stop — The officer must have had reasonable articulable suspicion before initiating the stop. An unlawful stop suppresses all subsequent evidence.
- Field sobriety test administration — NHTSA protocols govern all three Standardized Field Sobriety Tests. Deviations from these protocols undermine their validity.
- Challenging officer observations — In DWI cases relying entirely on behavioral evidence, the officer's subjective observations can be challenged through cross-examination and body camera footage.
- BWC and MVR inconsistencies — If the video does not show what the officer reported, that inconsistency is powerful evidence at trial.
- Medical or environmental explanations — Bloodshot eyes, unsteady gait, and slurred speech can have innocent medical explanations unrelated to alcohol consumption.