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Montana DUI Laws

DUI Defense in Montana

Statutes, Penalties, and Defense Strategies

What you are facing, the deadlines that bind you, and the questions an attorney needs to answer — under Montana (MT) DUI law.

BAC Limit

0.08

Enhanced BAC

0.16

Higher penalties above this

Lookback Period

10 years

Prior offenses count within

First Offense Penalties in Montana

Jail TimeUp to 6 months (mandatory 24 hours if BAC 0.16+)
Fines$600 – $1,000
License Suspension6 months
Ignition Interlock

Plain language

A breath-tester wired into the car ignition. The car will not start without a clean sample.

Required for BAC 0.16+

Implied Consent and Test Refusal

Montana has an

implied consent law

Plain language

By driving on the state's roads, you have already agreed to a chemical test if an officer has probable cause to think you are impaired.

like every state. The test can be breath, blood, or urine. Refusing carries its own penalty, listed below.

Refusal Penalty

6-month license suspension

Montana-Specific Detail

Montana has no mandatory minimum jail time for a standard first-offense DUI (under 0.16 BAC). The state does require a chemical dependency assessment and completion of a treatment course.

Is your Montana DUI defense on track?

The Masked Researcher’s First Read checks 10 critical defense behaviors specific to DUI cases. Takes 2 minutes. Instant results.

Take the Free Defense Score

DUI Defense Playbook — $127

26 questions that change how your next attorney meeting goes, a case stage roadmap, red flag checklist, and a case progress scorecard. Instant PDF download — calibrated for Montana DUI defendants.

Get the DUI Playbook — $127Read the Free DUI Guide

Other Montana defense topics

Facing a different charge in Montana? Penalty ranges, enhancements, and defense questions for related crimes:

Drug Possession in MontanaAssault in MontanaDomestic Violence in Montana

Important: This page provides general legal information about Montana DUI laws as of the date of publication. Laws change frequently. This is not legal advice. For guidance specific to your case, speaking with a Montana-licensed attorney is one option, or take the free Masked Researcher’s First Read to see where your case stands.