Montana DUI statute (Mont. Code Ann. sec. 61-8-401), per se BAC limit (0.08%), penalties for first through fourth DUI, mandatory IID after first conviction, and the 80 mph speed limit context for rural Montana DUI enforcement

Montana DUI law -- penalties and basics: (1) Montana DUI offense -- Mont. Code Ann. sec. 61-8-401: a person commits DUI if, while operating or in actual physical control of a vehicle, the person is "under the influence of alcohol, a dangerous drug, or any combination thereof" -- meaning the person's ability to safely operate a vehicle is impaired. Montana also has a per se DUI: BAC of 0.08% or more (21+) satisfies the offense without proof of impairment beyond the BAC level; (2) First DUI penalty: (a) up to 6 months in jail (minimum of 24 hours; the minimum may be suspended if the defendant participates in a 24-hour community service program); (b) $600 to $1,000 fine; (c) 6-month license suspension; (d) mandatory alcohol/drug treatment assessment; (e) mandatory IID (ignition interlock device) after license reinstatement for the period of the suspension (extended IID requirement after first conviction implemented in recent years); (3) Second DUI (within 10 years): (a) minimum 7 days in jail (maximum 1 year); (b) $1,200 to $2,000 fine; (c) 1-year license suspension; (d) mandatory IID for at least 1 year after reinstatement; (e) mandatory treatment; (4) Third DUI (within 10 years): felony in Montana; (a) minimum 30 days in prison; (b) $2,500 to $5,000 fine; (c) 1-year suspension; (d) IID; (5) Fourth and subsequent DUI (felony): permanent revocation is possible; (6) Montana DUI in the 80 mph context: Montana's high rural interstate speed limit (80 mph; enacted 2015) and the vast distances between cities mean that drivers who drink in Missoula and then drive to Billings (344 miles east on I-90) or from Billings to Great Falls (225 miles north on US-87 or I-15) may be driving long distances at high speeds on rural interstates after drinking. This geographic reality creates particularly dangerous conditions and has been a focus of Montana Highway Patrol enforcement campaigns on I-90 and I-15 during summer and holiday weekends.

Montana implied consent (Mont. Code Ann. sec. 61-8-402), blood draw without warrant (State v. Claassen, 2012 MT 313; Birchfield v. North Dakota, 579 U.S. 438 (2016)), administrative license suspension (ALS), and DUI on Montana Indian reservations

Montana DUI procedure and special issues: (1) Montana implied consent -- Mont. Code Ann. sec. 61-8-402: a driver who operates a vehicle in Montana is deemed to have consented (implied consent) to a chemical test (breath; blood; urine) if lawfully arrested for DUI. Refusal of the chemical test triggers: (a) an administrative license suspension of 182 days for the first refusal; (b) the refusal may be admitted as evidence of guilt at the DUI trial (refusal evidence = consciousness of guilt inference); (c) the driver faces both the administrative suspension AND the underlying DUI criminal charge; (2) Blood draw without warrant -- State v. Claassen, 2012 MT 313, and Birchfield: the Montana Supreme Court's analysis in Claassen addressed the circumstances under which law enforcement may compel a warrantless blood draw for DUI evidence. The US Supreme Court's decision in Birchfield v. North Dakota, 579 U.S. 438 (2016) subsequently held that: (a) warrantless breath tests incident to arrest for DUI are constitutional (a breath test is a minimal intrusion); (b) warrantless blood draws incident to arrest for DUI are NOT constitutional (a blood draw is a greater intrusion; a warrant is generally required). After Birchfield, Montana law enforcement must obtain a warrant before compelling a blood draw in most DUI arrests, unless exigent circumstances apply (the DUI suspect's rapidly dissipating BAC may satisfy exigency in some circumstances); (3) Administrative license suspension (ALS) -- Montana Motor Vehicle Division: the ALS system operates separately from criminal DUI proceedings. A driver who fails a breath test (0.08%+ BAC) or refuses the test receives a temporary license (valid 7 days) and notice of the ALS. The driver has 30 days to request a hearing before the Montana Motor Vehicle Division to contest the ALS. ALS grounds for challenge: (a) whether the officer had reasonable grounds to request the test; (b) whether the driver was given proper implied consent warnings; (c) whether the test was properly administered; (4) DUI on Montana Indian reservations: Montana's seven Indian reservations present complex DUI enforcement jurisdiction questions. On reservation roads: (a) tribal police have authority to arrest tribal member DUI suspects; (b) state law enforcement (Montana Highway Patrol; county sheriffs) may lack authority to arrest non-Indian suspects on reservation roads unless a Public Law 280 arrangement applies (Montana is not a full PL-280 state); (c) the federal "Major Crimes Act" (18 U.S.C. sec. 1153) applies to major criminal offenses by Indians against Indians on reservation land, but DUI is generally not a "major crime" within the Act's scope; (5) Montana CDL DUI: commercial driver's license holders face a mandatory 1-year CDL disqualification for any DUI conviction (in any vehicle; CDL commercial operation or personal vehicle). CDL holders may not drive commercial vehicles with a BAC of 0.04% or more. Lifetime CDL disqualification after a second DUI. Given Montana's significant commercial trucking industry (I-90; BNSF Railway support vehicles; agricultural transport), CDL DUI is a significant employment consequence.

Montana speeding on I-90 and US-2 (Hi-Line), deer and elk vehicle collision traffic law, and Montana's open container law (Mont. Code Ann. sec. 61-8-460)

Montana traffic law distinctive issues: (1) Montana speeding -- I-90 and the 80 mph context: Montana's 80 mph rural interstate speed limit (the highest in the US) means that speeding violations begin only above 80 mph on rural interstates. On two-lane US highways (US-2; US-12; US-87; US-191), the speed limit is typically 70 mph. Montana Highway Patrol (MHP) enforces speed limits primarily on I-90 (the east-west interstate through southern Montana) and I-15 (the north-south interstate through Great Falls, Helena, and Butte). Speeding fines in Montana are graduated based on how far over the limit the driver is traveling -- excessive speed (reckless driving speed) may be charged as the criminal offense of reckless driving; (2) Montana reckless driving -- Mont. Code Ann. sec. 61-8-301: reckless driving (driving in willful or wanton disregard for the safety of persons or property) is a misdemeanor in Montana (first offense: up to 90 days in jail and a $300 fine). Reckless driving charges frequently arise from: high-speed passes on two-lane highways; driving in dangerous conditions at unsafe speeds (mountain passes during winter storms; Glacier NP's Going-to-the-Sun Road in poor visibility); (3) Montana open container law -- Mont. Code Ann. sec. 61-8-460: Montana prohibits open containers of alcohol in the passenger area of a motor vehicle on a public highway. The open container law is consistent with federal highway funding requirements (the Transportation Equity Act for the 21st Century; 23 U.S.C. sec. 154). Violations are infraction-level offenses in Montana. Note: Montana has historically had a more permissive drinking culture than many states, and drive-through liquor stores and bar culture are significant features of small-town Montana life; (4) Montana's wildlife collision and duty to report: a driver who collides with a deer, elk, or other big game animal in Montana is not required to report the collision to law enforcement -- however, the driver may legally retain the meat of a deer or elk killed in a collision if the driver contacts Montana Fish, Wildlife and Parks within a reasonable time. This is unlike the "leave the animal" standard in some states -- Montana recognizes the practical and resource conservation value of harvesting game killed in vehicle collisions; (5) Montana motorcycle and ATV regulations: Montana requires helmets only for riders under 18 (adults may ride without helmets). Montana has extensive ATV and off-highway vehicle (OHV) trail networks -- ATVs are permitted on many Montana county roads and forest roads. ATV-related traffic violations (operating an OHV on prohibited roads; operating without lights) and ATV accidents on public roads are a distinct Montana traffic enforcement category.

DUI & Traffic Laws in Montana (2026)

A clearer Montana DUI & Traffic Violations page: dashcam preservation, stop record, and before timing gets tighter

Clearer statewide dui & traffic violations guidance for Montana built around dashcam preservation, the review moments that actually change outcomes, and the official path readers usually need first.

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Key Takeaways

Montana DUI: Mont. Code Ann. sec. 61-8-401; "under the influence" = ability to safely operate vehicle impaired by alcohol or drugs; per se: 0.08%+ BAC (21+) + 0.04% (CDL) + any detectable amount (under 21). First DUI: 24 hours minimum to 6 months jail (minimum suspendable for 24-hour community service) + $600-$1,000 fine + 6-month license suspension + alcohol/drug assessment + MANDATORY IID after first conviction (expanded from prior law). Second DUI (within 10 years): 7+ days jail (minimum) + $1,200-$2,000 fine + 1-year suspension + mandatory IID 1+ year after reinstatement + mandatory treatment. Third DUI (within 10 years): FELONY; 30+ days prison + $2,500-$5,000 fine + 1-year suspension + IID. Fourth+ DUI: felony; possible permanent revocation. 80 MPH CONTEXT: Montana rural interstate 80 mph (highest in US; enacted 2015); vast distances (Missoula to Billings = 344 miles on I-90; Billings to Great Falls = 225 miles on US-87/I-15); long-distance rural interstate driving after drinking = severe accident risk; MT Highway Patrol DUI enforcement campaigns on I-90 + I-15 during summer/holiday weekends.
Implied consent: Mont. Code Ann. sec. 61-8-402; lawful DUI arrest = deemed consent to breath/blood/urine test. Refusal: 182-day ALS (first refusal) + refusal evidence admissible at trial (consciousness of guilt). Warrantless blood draw: Birchfield v. North Dakota, 579 U.S. 438 (2016) = breath test incident to arrest CONSTITUTIONAL (minimal intrusion) + blood draw incident to arrest NOT constitutional (greater intrusion; warrant generally required); Montana State v. Claassen, 2012 MT 313 (pre-Birchfield MT Supreme Court analysis); post-Birchfield = MT law enforcement must get warrant before blood draw in most DUI arrests (exigency = rapidly dissipating BAC may apply in some cases). ALS (Montana Motor Vehicle Division): fails test (0.08%+ BAC) or refusal = 7-day temporary license + ALS notice; 30 days to request MVD hearing; ALS challenge grounds = reasonable grounds for test request + proper implied consent warnings + proper test administration. DUI on MT reservations: tribal police = authority over tribal member DUI; MHP/county sheriffs may lack authority over non-Indians on reservation roads (MT not full PL-280 state); DUI generally not "major crime" under Major Crimes Act (18 U.S.C. sec. 1153). CDL DUI: 1-year CDL disqualification for ANY DUI (personal or commercial vehicle); lifetime CDL disqualification after 2nd DUI; CDL BAC limit = 0.04%; significant employment consequence for MT trucking industry + agricultural transport.
Montana speeding: 80 mph rural interstate (violations begin above 80 mph); 70 mph typical two-lane US highways (US-2/US-12/US-87/US-191); MHP enforcement on I-90 (east-west through southern MT) + I-15 (Great Falls/Helena/Butte); graduated fines based on mph over limit; excessive speed = reckless driving criminal charge. Reckless driving: Mont. Code Ann. sec. 61-8-301 (willful/wanton disregard for safety); misdemeanor (first offense: up to 90 days jail + $300 fine); common scenarios = high-speed passes on 2-lane highways + driving at unsafe speeds in dangerous conditions (mountain passes winter storms + Going-to-the-Sun Road poor visibility). Open container: Mont. Code Ann. sec. 61-8-460; prohibited in passenger area of vehicle on public highway; infraction-level; federal TEA-21 (23 U.S.C. sec. 154) compliance. WILDLIFE COLLISION MEAT RECOVERY: driver colliding with deer/elk/big game in MT NOT required to report collision; MAY LEGALLY RETAIN MEAT if contacts MT Fish, Wildlife and Parks within reasonable time (practical resource conservation approach unique to MT; contrast with "leave the animal" standard in some states). Motorcycle: helmets required only for under-18 (adults choose; no requirement). ATV/OHV: extensive MT county road + forest road ATV networks; OHV violations (prohibited road use; no lights) = distinct MT traffic enforcement category.

Key Numbers — Montana All 50 states →

Filing Deadline 3 years

Fault Rule Modified Comparative

Insurance System At-Fault

Key Statute Mont. Code Ann. § 27-2-204

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Montana DUI law (Mont. Code Ann. sec. 61-8-401 et seq.) operates in a state with 80 mph rural interstate speed limits, vast distances between cities, and a cultural context that has historically been more tolerant of drinking and driving than coastal urban states -- contributing to Montana's status in many years as one of the US states with the highest DUI arrest and traffic fatality rates per vehicle mile traveled. Montana defines the DUI offense broadly: "under the influence" means the person's ability to safely operate a vehicle is impaired by alcohol or drugs. The per se BAC limit is 0.08% for drivers 21 and over, 0.04% for CDL commercial drivers, and any detectable amount for drivers under 21. Montana's DUI law has been significantly strengthened over the past two decades in response to high fatality rates -- ignition interlock devices (IIDs) are now required after the first DUI conviction for all eligible offenders (an expansion from prior law).

Montana's administrative license suspension (ALS) system operates separately from DUI criminal proceedings. The Montana Department of Justice Motor Vehicle Division handles administrative suspensions for failing a chemical test (90-day first offense ALS) or refusing a test (182-day first offense ALS for refusal). The leading Montana DUI Supreme Court decision is State v. Claassen, 2012 MT 313, which addressed the circumstances under which an officer may compel a blood draw without a warrant (a significant issue given the Supreme Court's later decision in Birchfield v. North Dakota, 579 U.S. 438 (2016), which held that warrantless blood draws incident to DUI arrest are unconstitutional but warrantless breath tests are permissible). Montana's implied consent law (Mont. Code Ann. sec. 61-8-402) requires submission to a breath, blood, or urine test after a lawful DUI arrest.

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