Montana's rule on DUI penalties turns on a feature the national template does not capture: BAC limits: 0.08% for adults; 0.04% for commercial drivers; zero-tolerance for drivers under 21. A first offense: First-offense DUI is typically a misdemeanor with fines, possible jail, license suspension, chemical-dependency assessment, and ignition-interlock conditions. Felony threshold: A fourth DUI can be a felony; DUI with serious bodily injury or death can also be a felony. The controlling authority is Mont. Code Ann. § 61-8-1002. Lookback: Prior DUI convictions within 10 years enhance penalties under Montana’s impaired-driving code.. Ignition interlock: Ignition interlock may be required for probationary licenses after DUI.
Key takeaways
- BAC limits: 0.08% for adults; 0.04% for commercial drivers; zero-tolerance for drivers under 21
- Lookback period: Prior DUI convictions within 10 years enhance penalties under Montana’s impaired-driving code.
- First-offense range: First-offense DUI is typically a misdemeanor with fines, possible jail, license suspension, chemical-dependency assessment, and ignition-interlock conditions.
- Felony threshold: A fourth DUI can be a felony; DUI with serious bodily injury or death can also be a felony.
- Ignition interlock: Ignition interlock may be required for probationary licenses after DUI.
- Primary authority: Mont. Code Ann. § 61-8-1002.
Worked example under Montana law
The illustration below uses only rules already stated for Montana. It is a research hypothetical, not a prediction of what a court will do.
A driver in Montana is charged with a first impaired-driving offense and wants to know what the statute actually sets.
- Start with the alcohol limits: 0.08% for adults; 0.04% for commercial drivers; zero-tolerance for drivers under 21
- Read the first-offense range: First-offense DUI is typically a misdemeanor with fines, possible jail, license suspension, chemical-dependency assessment, and ignition-interlock conditions.
- Ask when the charge becomes a felony: A fourth DUI can be a felony; DUI with serious bodily injury or death can also be a felony. Lookback: Prior DUI convictions within 10 years enhance penalties under Montana’s impaired-driving code.
- Interlock: Ignition interlock may be required for probationary licenses after DUI.
Montana DUI under § 61-8-1002 proceeds in justice or district court with parallel Motor Vehicle Division actions.
Blood alcohol limits in Montana
0.08% for adults; 0.04% for commercial drivers; zero-tolerance for drivers under 21
Lookback window for prior offenses
Prior DUI convictions within 10 years enhance penalties under Montana’s impaired-driving code.
First-offense penalties
First-offense DUI is typically a misdemeanor with fines, possible jail, license suspension, chemical-dependency assessment, and ignition-interlock conditions.
When a Montana DUI becomes a felony
A fourth DUI can be a felony; DUI with serious bodily injury or death can also be a felony.
Ignition interlock and license consequences
Ignition interlock may be required for probationary licenses after DUI.
How a typical Montana DUI case unfolds
Montana DUI under § 61-8-1002 proceeds in justice or district court with parallel Motor Vehicle Division actions.
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Case law: DUI penalties in Montana
STATE OF MONTANA, City of Bozeman, Plaintiff and Respondent, v. ROBERT PETERSON, Defendant and Appellant
…ivered the Opinion of the Court. Defendant was convicted of driving under the influence of alcohol by the District Court, Eighteenth Judicial District, Gallatin County. We reverse and dismiss the judgment of the District Court. At approximately 2:00 a.m., on March 23, 1985, Robert D. Peterson was arrested in Bozeman, Montana, for driving under the influence of alcohol. He made…
Montana opinions such as STATE OF MONTANA, City of Bozeman, Plaintiff and Respondent, v. ROBERT PETERSON, Defendant and Appellant are cited where DUI penalties is disputed. The court stated: "Opinion of the Court. Defendant was convicted of driving under the influence of alcohol by the District Court, Eighteenth Judicial District, Gallatin County. We reverse and dismiss the judgment of the District Court. At approximately 2:00 a.m., on March 23, 1985, Robert D." That is the language to brief; the rest of the decision supplies the procedural posture.
STATE OF MONTANA, Plaintiff and Respondent, v. JOHN E. LEE, Defendant and Appellant
…h Judicial District, Missoula County, finding Lee guilty of driving under the influence of alcohol. We affirm. The following issue is presented for our review: Did the District Court err in ruling that there was sufficient probable cause to arrest the defendant for driving under the influence of alcohol? The record discloses the following pertinent facts. On the evening of Sept…
Practitioners open STATE OF MONTANA, Plaintiff and Respondent, v. JOHN E. LEE, Defendant and Appellant when Montana DUI penalties turns on the distinction in this sentence: "Judicial District, Missoula County, finding Lee guilty of driving under the influence of alcohol. We affirm." Do not lift it out of the facts the court was deciding.
The STATE OF MONTANA, Plaintiff and Respondent, v. ROBERT RAYMOND McDONALD, Defendant and Appellant
…Opinion of the Court. Defendant appeals his conviction for driving under the influence, a violation of section 61-8-401, MCA, following a bench trial in the District Court of the Sixth Judicial District, Park County. Claiming that the State failed to comply with full discovery and failed to lay a proper foundation for the admission of a blood alcohol test report and testimony,…
Practitioners open The STATE OF MONTANA, Plaintiff and Respondent, v. ROBERT RAYMOND McDONALD, Defendant and Appellant when Montana DUI penalties turns on the distinction in this sentence: "Opinion of the Court. Defendant appeals his conviction for driving under the influence, a violation of section 61-8-401, MCA, following a bench trial in the District Court of the Sixth Judicial District, Park County." Do not lift it out of the facts the court was deciding.
In Re the Matter of the SUSPENSION OF THE DRIVING PRIVILEGES of CRAIG F. ORMAN
In Re the Matter of the SUSPENSION OF THE DRIVING PRIVILEGES of CRAIG F. ORMAN, 224 Mont. 332 (1986)
…the Opinion of the Court. *333 Craig Orman was arrested for driving under the influence of alcohol. At the time of his arrest he refused to submit to a breath test to determine the level of his intoxication. The Department of Justice suspended Mr. Orman’s driver’s license for one year because the breath test refusal was his second such refusal in Montana within the past five ye…
On DUI penalties, In Re the Matter of the SUSPENSION OF THE DRIVING PRIVILEGES of CRAIG F. ORMAN speaks to the Montana dispute in this passage: "Opinion of the Court. *333 Craig Orman was arrested for driving under the influence of alcohol. At the time of his arrest he refused to submit to a breath test to determine the level of his intoxication. The Department of Justice suspended Mr." The surrounding opinion shows how the court applied that language to the record.
STATE OF MONTANA, Plaintiff and Respondent, v. STEVEN RICHARD PALMER, Defendant and Appellant
…er? 2. Was the evidence sufficient to find Palmer guilty of driving under the influence of alcohol? I. This case involves a fourteen-mile high speed car chase by three police officers, reminiscent of a “Dukes of Hazard” television episode. At approximately 2:30 a.m. on September 11, 1988, Officer David Reynolds of the Gallatin County Sheriff’s Department observed a car travelin…
Practitioners open STATE OF MONTANA, Plaintiff and Respondent, v. STEVEN RICHARD PALMER, Defendant and Appellant when Montana DUI penalties turns on the distinction in this sentence: "Was the evidence sufficient to find Palmer guilty of driving under the influence of alcohol?" Do not lift it out of the facts the court was deciding.
STATE OF MONTANA, Plaintiff and Respondent, v. LYNDA M. DOLAN, Defendant and Appellant
…convicted in Ravalli County Justice Court of the offense of driving under the influence of alcohol, in violation of § 61-8-401, MCA. She appealed to the District Court for the Twenty-First Judicial District in Ravalli County and moved to suppress evidence obtained from two blood tests. The District Court denied Dolan’s motion to suppress and denied her motion for reconsideratio…
On DUI penalties, STATE OF MONTANA, Plaintiff and Respondent, v. LYNDA M. DOLAN, Defendant and Appellant speaks to the Montana dispute in this passage: "Ravalli County Justice Court of the offense of driving under the influence of alcohol, in violation of § 61-8-401, MCA. She appealed to the District Court for the Twenty-First Judicial District in Ravalli County and moved to suppress evidence obtained from two blood tests." The surrounding opinion shows how the court applied that language to the record.
STATE OF MONTANA, Plaintiff and Respondent, v. RUSSELL MELVIN FREGIEN, Defendant and Appellant
…istrict Court, Gallatin County, with one felony *19count of Driving Under the Influence of Alcohol (fourth or subsequent offense) in violation of § 61-8-401, MCA, and with one misdemeanor count of Driving Without a Valid Driver’s License, in violation of § 61-5-102, MCA. Fregien pled not guilty and moved to suppress the blood test results obtained by the State via an investigat…
STATE OF MONTANA, Plaintiff and Respondent, v. RUSSELL MELVIN FREGIEN, Defendant and Appellant is worth reading on Montana DUI penalties because the court put the point in its own words: "Court, Gallatin County, with one felony *19count of Driving Under the Influence of Alcohol (fourth or subsequent offense) in violation of § 61-8-401, MCA, and with one misdemeanor count of Driving Without a Valid Driver’s License, in violation of § 61-5-102, MCA." Use that passage as the starting point, then read the facts that precede it.
CITY OF MISSOULA, Plaintiff and Appellee, v. AMBER ARMITAGE, Defendant and Appellant
…0.08. ¶9 Armitage was charged with negligent endangerment, driving under the influence of alcohol, operating a vehicle with expired registration, failure to carry proof of insurance, and operation of a noncommercial vehicle with a blood alcohol concentration of 0.08 or more. She filed a motion to suppress all evidence obtained as a result of the investigative stop. The Municip…
Practitioners open CITY OF MISSOULA, Plaintiff and Appellee, v. AMBER ARMITAGE, Defendant and Appellant when Montana DUI penalties turns on the distinction in this sentence: "Armitage was charged with negligent endangerment, driving under the influence of alcohol, operating a vehicle with expired registration, failure to carry proof of insurance, and operation of a noncommercial vehicle with a blood alcohol concentration of 0.08 or more." Do not lift it out of the facts the court was deciding.
Frequently asked questions
What is the legal BAC limit in Montana?
0.08% for adults; 0.04% for commercial drivers; zero-tolerance for drivers under 21
Is a first DUI a felony in Montana?
A fourth DUI can be a felony; DUI with serious bodily injury or death can also be a felony.
Will I need an ignition interlock device?
Ignition interlock may be required for probationary licenses after DUI.
This guide covers Montana impaired-driving law as of 2026. Sentencing grids, administrative DMV rules, and local diversion programs change — verify the live statute and speak with counsel about your charging document.