It is not uncommon when listening to audio from a DWI arrest or when speaking to a new client that they are confused that they needed to take more than one test for their blood alcohol content. The statement is always the same, “I already took a breath test on the road.” The test on the road is referred to as a preliminary breath test (PBT) and is not generally admissible into court unless a person refuses to take an evidentiary test. (Blood, Breath or Urine test requested during the implied consent process)
What is this mystical preliminary breath test? It is a small handheld device that an officer uses in an attempt to measure blood alcohol content by measuring the alcohol contained in your breath as you exhale. Because alcohol remains in the system until it is filtered out by the body’s natural processes, the air you exhale also contains traces of the substance. This trace amount of substance is measured by the PBT. This amount is then used to calculate the amount of alcohol in your system. Due to the inaccuracy of the PBT test it is not admissible in most DWI trials.
The machine most frequently confused with the PBT is the Intoxilyzer or more recently the DataMaster. They work in a similar fashion as the PBT measuring deep lung air for alcohol. The difference is that the results can be used in court, due to the so called accuracy. (Or so they tell you). The Intoxilyzer and DataMaster are commonly done in a police station after a reading of the implied consent advisory.
The question becomes should I take the PBT when requested by an officer. The short answer is no. Minnesota is not a “blow and go” state meaning if the officer has requested you take a PBT for all intents and purposes, a decision has been made that you are going to be placed under arrest for DWI. All the PBT is going to do is confirm the officer’s suspicion and be used at a pre-trial to validate the officer had probable cause to make the arrest.