Last updated on November 2, 2021

Roadside Breath Tests in Michigan

In Michigan, when a police officer stops a driver on suspicion of drunk driving or OWI, the officer can request field sobriety tests and/or a preliminary breath test (PBT). If a driver in Michigan refuses this test, the state may impose a fine of up to $150, plus court costs.

The roadside breath test, also called a preliminary breath test or PBT, indicates the presence and/or concentration of alcohol based on a breath sample. The purpose of the breath test and other field sobriety tests is to determine if there is probable cause to arrest you for driving under the influence.

While you can refuse to take the test, your refusal may not stop the officer from arresting you if there is other evidence of alcohol usage that would affect your ability to drive. If you refuse to take the PBT, you may be charged with a civil infraction, which carries a fine up to $150 plus court costs.

Whether you take the PBT or not, if you are then arrested for drunk driving, Michigan’s implied consent law requires you take a chemical (breath, blood or urine) test to determine blood alcohol level. If you refuse to take the test, or if the test shows that your BAC is 0.08 or higher, the police officer will destroy your driver license and issue a paper permit to you. You may drive on the paper permit until your criminal case is resolved in court.

Problems With Breath and Other Roadside Tests in Michigan 

Breath tests are a notoriously unreliable way of measuring blood alcohol content. Many roadside test machines are miscalibrated and not all police officers have the proper training to use them correctly. A breath test machine at the police station may be more accurate, but there can be serious problems because post-arrest alcohol absorption can distort the results.

In addition to miscalibration, other sources of error for the breath test machines include the cleanliness of the device and the hands of the officer giving the test, and the possibility of exposure to other sources of alcohol besides beverages.

The math used by Breathalyzer machines assumes your body temperature is a standard 98.6 degrees and that your blood’s cellular density range is 47 percent. A higher temperature or a person with “denser” blood can exaggerate your actual blood alcohol level.

Other roadside field sobriety tests must be administered by a properly trained officer and with strict adherence to protocol of the National Highway Transportation Safety Administration. Many officers do not have the training to conduct these tests properly. 

Roadside Breath Tests and Your Legal Case 

If you feel your preliminary breath or other roadside tests were not valid, you can dispute them in court. Your Michigan DUI defense attorney can raise doubts about the validity of these tests, and whether there was probable cause for your drunk driving arrest.

A Michigan DUI/OWI defense lawyer can challenge the results of your blood alcohol level by challenging the assumption that every human being has the same body chemistry as well as the calibration of the machine.

Posted in: DWI
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