Montana DUI Preliminary Screening Tests

If an officer has stopped you (because he had a particularized suspicion) he will then watch for any indications that you are under the influence of alcohol or drugs. Assuming that there are some indications, the officer will then perform a Preliminary Screening Test. These tests come in a number of different formats, and carry a different amount of weight in making a determination of whether to perform an arrest for DUI.

We’ve discussed Montana field sobriety tests before. These are one of the preliminary screening tests that officers use to determine whether you have been driving under the influence of alcohol or drugs. A videotape of the tests is admissible even if no Miranda Warnings have been given. And successfully performing the field sobriety test does not mean you can’t still be arrested for DUI. Montana courts have ruled that the tests are not required to establish probable cause for an arrest and that probable cause may still be established with other evidence.

The horizontal gaze nystagmus (HGN) test is really a field sobriety test, but common enough to warrant its own discussion. This is when an officer holds something in front of your face and moves it left and right asking you to follow it with your eyes. The officer is trained to watch the way your eyes move to determine whether you are impaired by alcohol. Although it seems simple enough, properly administering the HGN test requires a great deal of specialized knowledge, and before the results of one can be admitted into court, the evidence must show that the arresting officer was properly trained to administer the test and that he was administering it in accordance with that training.

The Preliminary Breath Test (PBT) is a portable breathalyzer that officers use at the scene of a traffic stop to establish probable cause for DUI arrest in Montana. If the officer has a particularized suspicion that a driver has consumed alcohol, Montana law allows him to request a PBT. The law is similar to the implied consent law, in that a refusal to take the PBT may result in the suspension or revocation of the driver’s license or privilege to drive. However, the results of these tests are not substantive evidence of the amount of alcohol present in a person’s body. They just provide an estimate of alcohol concentration for the purpose of establishing probable cause.

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