Quick answer: In Maryland, DUI “per se” means you can be convicted of driving under the influence based on your blood alcohol concentration (BAC) alone. If a valid test shows a BAC of 0.08 or more, the State does not have to prove that alcohol actually affected your driving — the number itself is the violation under Md. Code, Cts. & Jud. Proc. § 10-307(g) and Transp. § 21-902(a).
I’m David Waranch, and I’ve defended thousands of Maryland traffic and DUI cases. “Per se” is the part of the law most drivers misunderstand, so here is exactly what it means and why the number on the machine matters so much.
What Does “Per Se” Mean in a Maryland DUI?
“Per se” is Latin for “by itself.” In a DUI context it means the offense is proven by the test result by itself, without any separate proof that your driving was impaired. Under Cts. & Jud. Proc. § 10-307(g), a BAC of 0.08 or more means you are “under the influence of alcohol per se.” Maryland’s DUI statute, Transp. § 21-902(a)(1)(ii), then makes it a crime to drive while under the influence per se.
Put plainly: reach 0.08 and the law treats you as legally intoxicated no matter how you looked, walked, or spoke. The prosecutor does not need a bad performance on field sobriety tests, an officer’s opinion, or a witness. The reading is the case. For the bigger picture of how Maryland’s alcohol-driving laws fit together, see my full breakdown of Maryland DUI and DWI laws explained.
How Is DUI Per Se Different From an Impairment DUI or DWI?
Maryland actually gives the State two ways to prove a drunk-driving charge, and per se is only one of them:
- The per se route. A valid test of 0.08 or more. The number alone establishes guilt of DUI under § 21-902(a).
- The impairment route. Evidence that alcohol actually affected your ability to drive — the officer’s observations, your driving, and field sobriety tests. This is how the State proves an “under the influence” DUI when there is no test, and how it proves the lesser charge of driving while impaired (DWI) under § 21-902(b).
The BAC number itself sits on a ladder set by § 10-307. Where you land decides which presumption applies:
| BAC at time of test | What the law presumes |
|---|---|
| 0.05 or less | Presumed not under the influence and not impaired |
| More than 0.05, less than 0.07 | No presumption either way; considered with other evidence |
| At least 0.07, less than 0.08 | Prima facie evidence of driving while impaired (DWI) |
| 0.08 or more | Under the influence per se — DUI on the number alone |
So per se is the top rung. Below 0.08 the State has to work harder and argue impairment; at 0.08 and above, the machine has done the work for it unless you can knock the reading out.
Can the Number Alone Really Convict Me?
Yes. If the test result holds up, a judge or jury can convict you on that reading alone — even if you passed every field sobriety test and drove perfectly. That is the whole point of a per se law: it takes impairment out of the argument and replaces it with a number.
That is also why the fight in a per se case is usually a fight over the test itself, not over how you looked at the roadside. A defense often turns on questions like these:
- Was the breath or blood test administered correctly, by a qualified operator, on a properly maintained and calibrated instrument?
- Was the required observation period followed before the breath sample?
- Was the traffic stop itself legal? An unlawful stop can suppress the result that follows.
- Are there medical conditions, timing issues, or chain-of-custody gaps that undercut the number?
Undermine the reliability of the reading and the per se charge can fall apart, because there is nothing else holding it up. That’s the opposite of an impairment case, where the officer’s testimony can carry the State’s burden on its own.
“I passed the field sobriety tests, so I’m fine.” Not in a per se case. Doing well on the walk-and-turn or the one-leg stand does not erase a 0.08 reading — the number can convict you on its own. If you tested at or above 0.08, treat the case as serious and get the test result reviewed by a lawyer.
What Are the Penalties for a Per Se DUI?
A per se DUI is charged under § 21-902(a), the same subsection as an impairment-based DUI, so it carries the same criminal exposure:
| DUI under § 21-902(a) | Maximum jail | Maximum fine | MVA points |
|---|---|---|---|
| First offense | 1 year | $1,200 | 12 |
| Second offense (within 5 years) | 2 years | $2,400 | 12 |
A second offense within five years of a prior also carries a mandatory minimum of 5 days in jail. A DUI is a must-appear charge — there is no ticket you can just pay to make it go away, and paying or pleading guilty creates a criminal conviction. For a full first-timer walkthrough, see first-offense DUI penalties in Maryland, and for every tier read the complete Maryland DUI penalties guide.
Does the 0.08 Number Also Cost Me My License?
It can, and through a completely separate process. A 0.08 test triggers an administrative “per se” action by the MVA under Transp. § 16-205.1 that is independent of the criminal case. You are typically issued a 45-day temporary license at the stop, and you have just 10 days to request an Office of Administrative Hearings hearing to preserve all of your options. Miss that window and the suspension can take effect automatically.
Because the MVA case and the court case run on different tracks, you can beat one and still lose the other if you don’t act on both. I explain the administrative side in Maryland DUI license suspension lengths and what happens at the MVA per se hearing. If you refused the test instead of blowing a 0.08, the rules shift again — see can you refuse a breathalyzer in Maryland.
A per se charge is beatable, but it takes early, focused work on the test evidence and the MVA deadline. Talk to a Maryland DUI lawyer before either clock runs out.
Maryland DUI Per Se: Frequently Asked Questions
A blood alcohol concentration of 0.08 or more is DUI per se in Maryland. At that level, Cts. & Jud. Proc. 10-307(g) treats you as under the influence per se, so a valid test alone can support a DUI conviction under Transp. 21-902(a).
Yes. In a per se case the number is the offense, so doing well on field sobriety tests does not prevent a conviction. If a valid test shows 0.08 or more, a judge or jury can convict on that reading alone unless you can challenge the accuracy or legality of the test.
DUI per se is proven by a 0.08 or higher test result by itself, with no need to show impaired driving. DWI under Transp. 21-902(b) is the lesser charge of driving while impaired by alcohol, which the State proves with evidence that alcohol affected your driving, often at a BAC below 0.08.
Law Offices of David R. Waranch — 301-563-9575 · toll-free 1-877-566-2408. Hablamos Español.
Last updated: August 2026. Statutory references: Md. Code, Transp. § 21-902; Cts. & Jud. Proc. § 10-307; Transp. § 16-205.1. This page is general information about Maryland law, not legal advice, and reading it does not create an attorney-client relationship.