Montana DUI Laws and Penalties

Montana's DUI laws make it illegal to drive while under the influence of alcohol or drugs. This article covers how Montana law defines "under the influence" and the penalties you'll face for a DUI conviction.

How Montana's DUI Laws Define "Driving Under the Influence"

In Montana, a person can get a DUI for driving or being in actual physical control of a vehicle:

• with a blood alcohol concentration (BAC) of .08% or more
• with a THC (the psychoactive ingredient in marijuana) level of 5 ng/ml or more, or
• while under the influence of alcohol or any other drug which diminishes the person's ability to safely operate a vehicle.

Each of these prohibitions is considered a separate offense in Montana, and there are slight differences between the penalties depending on the type of DUI. (Mont. Code Ann. § 61-8-1002 (2024).)

How Montana Counts Prior DUI Convictions

The minimum and maximum jail time and fines you'll face for a DUI conviction in Montana largely depend on how many prior convictions you have. Two DUIs in ten years will result in a second DUI, while three in a lifetime will be a third offense.

More generally, a single DUI conviction that occurred more than 10 years ago doesn't count for purposes of sentencing on a second DUI conviction. However, once a driver has three DUI convictions, all priors count regardless of how long ago they occurred.

Jail Time and Fines for Montana DUI Convictions

Here are the possible jail sentences and fines for a first, second, and third DUI conviction in Montana.

Substance Abuse Assessments for Montana DUI Offenders

All DUI offenders must complete an evaluation to determine what treatment, educational classes, or other programs might be warranted to treat the driver's possible substance abuse issues. The evaluation is generally considered by the judge, and the convicted motorist must complete all court-ordered treatments before license reinstatement.

Probationary Licenses Following a Montana DUI Suspension

The judge is permitted to grant the convicted motorist the usage of a probationary license. This license permits the holder to drive for certain purposes but requires the use of an IID. Depending on the circumstances, the driver might be required to complete a certain portion of the suspension before being eligible for a probationary license.

Montana DUI Convictions and Vehicle Forfeiture

For a second or subsequent DUI, the judge can order vehicles owned by the defendant to be forfeited—meaning the vehicles would be taken and sold for the benefit of the state.

Montana's Aggravated DUI Law

Montana has an "aggravated DUI" classification that carries enhanced penalties. A DUI qualifies as an aggravated offense if:

• the driver's BAC is at least .16%
• the driver was subject to an IID requirement at the time of the DUI offense, or
• the driver had a DUI-related (including implied consent violations) suspended or revoked license when the DUI occurred.

Generally, drivers convicted of an aggravated DUI can expect more jail time and more expensive fines than would result from a regular DUI conviction.

Felony DUIs in Montana

In Montana, fourth and subsequent DUIs are felonies. For felony DUI convictions, the driver faces much more serious penalties. Depending on the situation, the driver could be looking at 13 months to 25 years in prison and up $10,000 in fines.