Drug-Impaired Driving in Montana
Driving under the influence isn’t only about alcohol. In Montana, you can be charged with a DUI if you’re operating a vehicle while impaired by prescription medication, over-the-counter drugs, or cannabis—even if your blood alcohol content (BAC) is under 0.08 %. Understanding how “drug-impaired driving” works is key to protecting your rights.
What counts as “drug-impaired driving” in Montana?
- Under Montana law, a driver may be charged with a DUI if they are under the influence of liquor, any drug, marijuana, a controlled substance, or any combination thereof to the extent that their ability to drive is materially and appreciably impaired.
- A BAC ≥ 0.08 % is not the only basis for DUI — you don’t need to be intoxicated on alcohol alone.
- Prescription medications (painkillers, sleep aids, anti-anxiety drugs), over-the-counter medications, and cannabis (even legal cannabis) may qualify if they impair your driving.
- The testing and evidentiary framework differ: drug detection, metabolite levels, field sobriety tests, officer testimony, and device calibrations all come into play.
Why this matters (and common misunderstandings)
- Many assume “I only took my prescription; I’m safe.” Not always. If the prescription caused impairment, you could face a DUI.
- Cannabis DUI is evolving in Montana — police have drug recognition experts, oral fluid tests, and video evidence increasingly in use.
- The consequences mirror alcohol DUIs: license suspension, possible jail, fines, ignition interlock, job and travel risks.
- Defense strategies differ: challenges often focus on the stop, field sobriety testing in drug cases, testing device accuracy, and medical conditions.
Steps the prosecution typically uses in drug-impaired driving cases
- Traffic stop / suspicion of impairment – The officer must have reasonable suspicion you were driving impaired (swerving, erratic speed, odor, etc.).
- Field sobriety tests / preliminary drug screening – One-leg stand, HGN (horizontal gaze nystagmus), other tests; sometimes breath test, rarely just for drugs.
- Chemical test for drugs or blood/urine – May include blood draw, oral fluid or urine. Chain of custody, calibration, metabolite timing are critical.
- Criminal charge & administrative license action – Even if results are pending, you may face administrative suspension for refusal or high levels.
- Defense/motion / plea or trial – Defense involves medical records, prescription history, stop legality, device validity.
What to Do If You’re Arrested for DUI in Missoula County.
What you should do if you’re involved in a drug-impaired driving arrest
- Ask for a lawyer immediately. Your rights and the time-sensitive administrative aspects matter.
- Do not volunteer excessive medical history but be prepared to compile records (prescriptions, underlying conditions).
- Document everything. Where were you stopped? What symptoms or behaviors did the officer point to? What prescription(s) do you take? Have you warned your doctor about driving?
- Preserve testing device records. Calibration logs, chain of custody, who administered the test.
- Request the administrative hearing. For Montana license issues tied to DUI, deadlines are tight and you don’t want to lose your driving privilege by default.
Montana DUI penalties for background on license suspension.
Specific challenges & strategies in Montana drug-DUI cases
- Prescription meds vs. impairment argument. Just because you have a prescription does not automatically mean you’re safe from impairment liability.
- Cannabis metabolite testing vs impairment. High metabolite levels don’t always equal current impairment—but prosecutors attempt to argue they correlate. Your defense may argue timing, tolerance and device accuracy.
- Field sobriety tests less reliable for drugs. Many field tests were developed for alcohol; drug impairment often manifests differently.
- Interplay with alcohol. Frequently, drug and alcohol use are both alleged; your defense must sort out which caused impairment.
- Administrative vs criminal separate tracks. Even if criminal charges are dropped or reduced, you may still face a license suspension from the DMV.
Clear next step
If you’re stopped and suspected of driving while impaired by drugs — legal, prescription, or illegal — the stakes are high and the rules are complex. Montana’s laws are not just about BAC. You need an attorney who understands how drug-impaired driving is handled in your county.
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