Montana’s DUI Laws and Conviction Penalties

The consequences of a 1st, 2nd, and 3rd DUI offense in Montana.

Like all states, Montana prohibits driving under the influence of drugs or alcohol. However, Montana's legal definitions for "driving" and "under the influence" differ from some other states.

This article explains these legal terms and also the various types of DUI charges and the possible penalties for a conviction.

Montana's DUI Laws

To establish a DUI charge in Montana, the prosecution must prove in court that the motorist was:

  • driving or in actual physical control of a vehicle, and
  • under the influence of drugs or alcohol.

However, these two elements require a bit more explanation.

How Montana's DUI Laws Define "Driving" or Being in "Actual Physical Control" of a Vehicle

DUI arrests are often preceded by a traffic stop. In such a case, there's no question that the motorist was driving a vehicle. But Montana DUI laws also extend to drivers in "actual physical control" of a vehicle, which, to the surprise of many, doesn't require actual movement of the vehicle.

Under Montana law, a driver is in actual physical control of a vehicle when he or she is in a position to cause the vehicle to move or control the vehicle's movement in some manner. Relevant factors for determining whether a motorist was in actual physical control often include where the motorist was seated, whether the ignition was on, where the vehicle was parked, and whether the vehicle was disabled in some way.

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

In Montana, the prosecution can establish a driver was "under the influence" by proving actual impairment or an excessive blood alcohol concentration (BAC) or tetrahydrocannabinol (THC) concentration.

Montana DUI Charges Based on Actual Impairment

Generally, a driver is considered to be under the influence of drugs or alcohol if his or her ability to safely operate a vehicle is diminished. Prosecutors will often use officer testimony and expert witnesses to establish a lack of coordination and other indicators of impairment.

Montana DUI Charges Based on BAC or THC (Per Se DUIs)

A driver can also be convicted of DUI for having an unlawful BAC or THC concentration. These "per se DUI" charges don't require proof that the driver was stumbling or physically incapable of driving. All the prosecution needs to prove to establish a per se DUI charge is that the driver had:

  • a BAC of .08% or more, or
  • at least five nanograms of THC per milliliter of blood in his or her body.

A physician's prescription can provide a defense to a per se THC charge but not a DUI charge based on actual impairment. In other words, you might be okay if you test positive for the medical marijuana you used last week, but if you're actually impaired at the time of the DUI arrest, the defense won't help.

Penalties for a 1st, 2nd and 3rd DUI Conviction in Montana

The penalties for a Montana DUI are set by statute, but judges generally have some discretion within these statutory limits. The penalty ranges generally depend on the number of prior convictions the driver has and whether certain aggravating factors are present.

How Long DUI Priors Stay on Your Record in Montana

A DUI will only be considered a second offense if it occurred within ten years of the first. However, for purposes of determining whether a DUI is a third or subsequent offense, all prior DUI convictions within the driver's lifetime are counted.

Jail Time and for Montana DUI Convictions

All DUI convictions result in fines and possible jail time. These are the standard penalties for a misdemeanor DUI (first, second, and third) conviction.

1st Offense

2nd Offense

3rd Offense


Up to 6 months

5 days to 1 year

30 days to 1 year


$600 to $1,000

$1,200 to $2,000

$2,500 to $5,000

Substance Abuse Treatment for Montana DUI Offenders

All persons convicted of a DUI offense are required to complete a chemical dependency assessment to determine the extent of any possible chemical dependencies. Based on the assessment, the court can order the offender to complete a chemical dependency treatment program.

A first-offense DUI requires a chemical dependency education course, but subsequent convictions generally require the completion of a residential alcohol treatment program as well as a one-year sobriety monitoring program.

Offenders who were under the influence of THC will have their marijuana registry identification card revoked.

DUI Probation in Montana

Instead of requiring jail time, judges will often place DUI offenders on probation. Probation requires the offender to comply with certain supervision rules such as random testing, treatment, and a 24/7 sobriety program (if available).

However, offenders must serve the minimum jail period prior to beginning probation. A driver must serve at least 24 hours in jail for a first offense, five or seven days in jail for a second offense, and 30 days in jail for a third offense.

Some jurisdictions offer "DUI Court," which serves as a more intensive probation program. It may be possible to avoid the minimum jail requirements by participating in the DUI Court program.

Montana's Enhanced DUI Penalties for Child Passengers

An impaired driver who was transporting a passenger under 16 years old will face increased penalties. As with an aggravated DUI (explained below), having a child passenger will generally double the potential penalties (although not the maximum jail time for a second or third offense).

Montana's "Aggravated" DUI Penalties

A driver who had a BAC of .16% or more, refused a chemical test (explained later), or had a suspended or restricted license for a prior DUI at the time of the present offense can be convicted of an aggravated DUI.

The jail time and fines for an aggravated DUI are as follows.

1st Offense

2nd Offense

3rd Offense


2 days to 1 year (4 days if child passenger)

15 days to 1 year (45 days if child passenger)

40 days to 1 year (90 days if child passenger)


$1,000 ($2,000 if child passenger)

$2,500 ($5,000 if child passenger)

$5,000 ($10,000 if child passenger)

Montana's Felony DUI Penalties

A DUI will be considered a felony if the offender has at least three prior DUI convictions or if the offender has a prior vehicular homicide conviction.

A felony DUI generally carries 13 months to two years in prison, followed by five years of probation, as well as $5,000 to $10,000 in fines. Probation requires that the offender complete an outpatient treatment program, avoid consuming alcohol or going to bars, and submit to random testing and sobriety monitoring. Alternatively, the offender may be eligible for a five-year court treatment program in lieu of the required prison sentence.

License-Related Penalties for Montana DUI Offenses

The license penalties and restrictions for a DUI incident generally vary based on the number of prior offenses and other aggravating factors. Additionally, under Montana's implied consent law, license-related penalties can result from a DUI arrest and/or conviction.

Montana's Implied Consent Law

Montana's "implied consent" law generally requires all drivers who are lawfully arrested for driving under the influence to submit to chemical testing when requested to do so by an officer. Required tests might include blood draws and breathalyzers.

Refusing a DUI Test in Montana

When a driver refuses to take an alcohol or drug test as required by the implied consent law, the officer will seize the driver's license and send a notice to the Department of Justice (DOJ). The driver's license will be suspended for six months and he or she must pay a $300 fee. Drivers with prior DUI incidents (within five years) will be suspended for one year.

Drivers who refuse testing are not eligible for restricted driving privileges.

License Revocation for DUI Convictions in Montana

At sentencing for a DUI conviction, the judge will order the driver's license be suspended. The suspension is six months for a first offense and one year for any subsequent violations. Drivers convicted of felony DUI will have driving privileges revoked for the duration of probation.

Montana's Ignition Interlock Device (IID) Requirements

During sentencing, the court is authorized to grant the convicted driver a probationary license. The license is generally limited to use during restricted times and locations and only with an installed IID.

A driver convicted of a second or subsequent DUI must complete a portion of the suspension period prior to obtaining a restricted license (45 days for a second DUI and 90 days for a third-offense DUI).

Montana's Underage DUI Law

Montana prohibits any person under the age of 21 years of age from driving or being in actual physical control of a vehicle with a BAC of at least .02%. Underage offenders face the following penalties:

  • a first offense will result in a $100 to $500 fine and a 90-day license suspension
  • a second offense carries a $200 to $500 fine, up to 10 days in jail, and six-month license suspension, and
  • a third or subsequent offense results in a $300 to $500 fine, 24 hours to 60 days in jail, and a one-year license suspension.

All offenders are also required to complete the chemical education dependency course and chemical dependency program.

DUI Plea Negotiations and Diversions

Montana has multiple options for drivers facing DUI charges. Both the 24/7 Sobriety program and the DUI diversion program can greatly reduce conviction penalties. In some cases, an accused motorist might also have some good defenses to fight the charges in court. Speak with a local attorney regarding your best options.

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