Montana law does not require a driver to perform field sobriety tests, and the implied consent statutes do not suspend a license for declining them. The Montana Supreme Court treats these tests as a search, which means an officer needs particularized suspicion of impaired driving before giving them. Declining is not free of consequences, though: it does not stop an arrest, and it is a different decision from refusing a breath test. This page explains the rules. It is part of our Montana DUI Guide.
Field Sobriety Tests Are a Search in Montana
Some courts elsewhere have held that roadside tests are not a search at all. Montana takes the opposite view. In Hulse v. State, 1998 MT 108, 289 Mont. 1, the Court held that field sobriety tests are searches under the Fourth Amendment and under Article II, Section 11 of the Montana Constitution, and that they "must also be based upon particularized suspicion."
The Court chose particularized suspicion over the higher probable cause standard, reasoning that the State's interest in getting impaired drivers off the road outweighs the limited intrusion. But the suspicion has to be about impaired driving, not only about the reason for the stop. The Court's own examples:
- A stop for erratic driving, such as weaving across the center line and the fog line, supports both the stop and the tests.
- A stop for a broken taillight, with no signs of intoxication when the officer reaches the window, does not. The officer "would be prohibited from administering field sobriety tests."
- A stop for a broken taillight where the officer then smells alcohol, or sees bloodshot and glassy eyes, or hears slurred speech, creates a separate particularized suspicion, and the tests may be given.
If the tests were given without that separate suspicion, the results can be challenged with a motion to suppress (MCA § 46-13-302).
No Statute Requires You to Perform Them
Montana's implied consent law says a person who drives on the ways of this state open to the public is considered to have consented to a test of blood, breath, or oral fluid (MCA § 61-8-1016(1)(a)). The suspension that follows a refusal is tied to those tests: the department suspends a license when it receives a report that a person refused a test of blood, breath, oral fluid, urine, or other bodily substance (MCA § 61-8-1032(1)).
Walking a line, standing on one leg, and following a pen with your eyes are not on that list. We have not found a Montana statute that makes declining them an offense or a license violation.
| Test | Legal basis | If you decline |
|---|---|---|
| Field sobriety tests (eye test, walk-and-turn, one-leg stand) | Not part of implied consent. A search that requires particularized suspicion of impaired driving (Hulse v. State, 1998 MT 108). | No license suspension in the implied consent statutes. The officer decides whether to arrest on the other evidence. |
| Roadside breath screen (PAST) | Covered by implied consent (MCA § 61-8-1016(1)(b)). | Can be reported as an implied consent refusal. See our roadside breath test page. |
| Breath, blood or oral fluid test after arrest | Covered by implied consent (MCA § 61-8-1016(1)(a)). | License suspension of 6 months or 1 year with no probationary license, and the refusal is admissible (MCA §§ 61-8-1032, 61-8-1018(2)). |
The middle row is where people get caught. The small handheld breath device offered at the roadside is an implied consent test, not a field sobriety test. See the roadside breath test.
What Declining Does Not Do
It does not prevent an arrest. An officer may arrest without a warrant on probable cause (MCA § 46-6-311(1)), and probable cause can come from driving, the odor of alcohol, speech, balance, and admissions. In City of Missoula v. Forest, 236 Mont. 129 (1989), no field sobriety tests were given. The Court called the tests "a tool" and held that their absence does not fatally flaw the probable cause determination. In State v. Van Kirk, 2001 MT 184, the driver declined the roadside tests because it was dark and the road surface was rough, and he was arrested on the officer's other observations.
It does not stop the breath test request. After an arrest, the officer will ask for a breath or blood sample under the implied consent law. That decision has its own consequences, explained on our test refusal page.
It may still be mentioned. The statutory refusal inference applies to implied consent tests (MCA § 61-8-1018(2)). The same statute says it does not limit other competent evidence on whether a person was under the influence (MCA § 61-8-1018(3)). A prosecutor may try to describe what you did and did not do at the roadside, and a judge decides what the jury hears.
No Lawyer and No Miranda Warning First
People often ask to call a lawyer before deciding. Montana law does not give that right at the roadside. In State v. Allen, 1998 MT 293, a driver who asked to consult his lawyer before roadside tests was told he could not, and the Court held no Miranda warning was required before the tests. In Van Kirk, the Court held the driver was not denied his right to counsel or his right against self-incrimination.
The reasoning is that the privilege against self-incrimination protects communications, not physical evidence. A request to perform sobriety tests, without questioning, is not custodial interrogation (State v. Thompson, 237 Mont. 384 (1989)). More on this in do I have to answer questions.
If You Did the Tests
Most people do, and the results are not beyond challenge. A report of a physical or psychomotor assessment is admissible only if it was made by a person trained by the Department of Justice or with training the department recognizes (MCA § 61-8-1018(1)(c)). For the eye test, Hulse requires more: before horizontal gaze nystagmus results come in, a qualified expert must explain the scientific basis for the link between alcohol and nystagmus. An officer trained only to give the test is not enough for that.
How each test is supposed to be given, and where officers go wrong, is covered in our pages on the horizontal gaze nystagmus test, the walk-and-turn, and the one-leg stand, and on our main field sobriety tests page.
An Honest Look at the Tradeoff
There is no answer that fits every driver. Performing the tests gives the officer scored observations and video, which can help or hurt depending on how you did and how the tests were given. Declining removes that evidence but leaves the officer to act on everything else, and it will not keep a suspicious officer from arresting. Nothing on this page is advice to do one or the other. If you have already been through a stop, what matters now is whether the officer had grounds to ask, and how the tests were actually administered.
This page explains Montana law in general as of the 2025 Montana Code Annotated and the court decisions cited. It is not legal advice about your specific case.