Field sobriety test evidence in a Montana DUI case is challenged on four grounds: whether the officer had a lawful basis to ask for the tests, whether the officer was trained and followed that training, whether the conditions allowed a fair test, and whether something other than alcohol explains the performance. Our field sobriety tests page describes the three tests. This page is about contesting them. It is part of our Montana DUI Guide.
The Tests Are a Search
In Hulse v. State, 1998 MT 108, 289 Mont. 1, the Montana Supreme Court held that field sobriety tests are not mere observations. They are a search under the Fourth Amendment and under Article II, Section 11 of the Montana Constitution (¶ 33), and like an investigative stop they must be based on particularized suspicion (¶ 38).
The Court explained how that works. Erratic driving can justify both the stop and the tests. But if an officer stops a driver only for a broken taillight and observes no signs of intoxication on contact, the officer would be prohibited from administering field sobriety tests. If the officer does observe signs such as the odor of alcohol, bloodshot and glassy eyes, or slurred speech, that is a separate particularized suspicion that allows them (¶¶ 39, 40).
So the first question is what the officer had seen, heard, and smelled before asking you to step out. See challenging the traffic stop.
Who May Testify About Them
By statute, a report of the facts and results of a physical, psychomotor, or physiological assessment is admissible if it was made by a person trained by the Department of Justice or by a person who has received training the department recognizes (MCA § 61-8-1018(1)(c)). The officer's training records are therefore part of the foundation and can be requested.
The horizontal gaze nystagmus test has an added requirement. Hulse held that an officer trained in the test may describe giving it and what was observed, but that the relationship between alcohol and nystagmus is beyond ordinary training, so the State must also present a witness qualified to explain that science (¶¶ 69 to 72). The Court has applied that rule since:
- State v. Michaud, 2008 MT 88, 342 Mont. 244. The State conceded it had not laid the foundation for the eye test. The Court held admitting it was an abuse of discretion and, because the State did not show the error was harmless, reversed (¶¶ 33 to 39).
- State v. Gieser, 2011 MT 2, 359 Mont. 95. Eye test testimony came in with no expert and no objection. The Court called the foundation rule "established" and reversed for ineffective assistance of counsel (¶ 10).
What the Officer Was Trained to Do
The standardized battery comes from training developed under the National Highway Traffic Safety Administration (NHTSA) and the International Association of Chiefs of Police. NHTSA's SFST Refresher participant manual (October 2015 revision) says the three tests "are designed to be administered and evaluated in a standardized manner." Some of what it tells officers:
| Test | What the manual describes | What a review checks |
|---|---|---|
| Horizontal gaze nystagmus | Three clues in each eye, six in total: lack of smooth pursuit, distinct and sustained nystagmus at maximum deviation, and onset before 45 degrees | Whether the eyes were first checked for equal pupil size, resting nystagmus, and equal tracking. The manual says unequal pupils or tracking may point to a medical disorder or injury |
| Walk and turn | An instructions stage and a walking stage of heel-to-toe steps. Clues include starting too soon, stopping while walking, and missing heel-to-toe | The surface. The manual calls for a reasonably dry, hard, level, non-slippery surface whenever possible, with room for nine steps |
| One leg stand | Four clues: swaying while balancing, using arms to balance, hopping, and putting the foot down | Footing, footwear, and any back, leg, or balance problem, compared with what the video shows |
The review is a comparison. The video is watched with the manual open: were the instructions given completely, was each test demonstrated, were the clues the officer recorded actually visible, and were things counted as clues that the manual says should not be. The manual notes, for example, that slight tremors of the foot or body should not be interpreted as swaying, and that walking slowly is not the same as stopping.
Conditions on the Roadside
The manual's preface is candid. Its procedures describe how the tests are to be given under ideal conditions. Such conditions do not always exist, and the manual says the tests will generally still serve as valid and useful indicators. It then adds that slight variations from the ideal "may have some effect on the evidentiary weight given to the results."
That sentence supports a conditions argument in Montana, where a test may be given on a gravel shoulder, on a grade, in wind, or on snow and ice. What to document:
- the surface, slope, and footing at the exact spot;
- temperature, wind, and precipitation;
- lighting, including patrol lights and passing headlights;
- your footwear. The manual says the original research suggests that people wearing heels more than 2 inches high should be given the opportunity to remove their shoes.
Medical and Physical Factors
The manual states that the original studies suggested individuals over 65 years of age, and people with back, leg, or inner ear problems, had difficulty performing the walk and turn, and it tells officers to consider all factors when conducting the tests. For the eye test, it describes categories of nystagmus not caused by alcohol, including nystagmus from disturbances of the inner ear and from pathological disorders such as brain damage or some diseases of the inner ear.
Medical records, a treating provider, or simply the video showing the same gait before and after the stop can support this. If you told the officer about a condition and were tested anyway, that belongs in the cross-examination. Our checklist of what to bring to a consultation lists what to write down.
What a Successful Challenge Changes
It depends on the charge. An impairment DUI under MCA § 61-8-1002(1)(a) often leans on the roadside tests, and in a drug case the State needs competent evidence of impairment beyond a positive test (MCA § 61-8-1018(1)(a)), so weakening the tests can matter a great deal. A per se charge rests on the number, and the roadside tests then matter mainly to whether the arrest was lawful. In Hulse itself the eye test should not have been admitted, yet the Court found the error harmless because of the other evidence (¶ 73). For the number, see challenging the breath test and challenging the blood test.
This page explains Montana law in general as of the 2025 Montana Code Annotated and the decisions cited, and quotes NHTSA's SFST Refresher participant manual (rev. 10/2015). Every case turns on its own facts, and past results do not predict future outcomes. It is not legal advice about your specific case.