Accuracy of Minnesota’s DWI Breath Test Machines under Recent Attack
In Minnesota, breath tests are the most common tests offered by law enforcement in a DWI arrest. But they are not the most accurate. Science has long shown that blood or urine testing for blood-alcohol content (BAC) produces much more accurate results. Thousands of people who are charged with DWI at or near the legal limit (.08), or twice the legal limit (.16) can face serious consequences from inaccurate and unreliable breath testing.
BCA Finally Releases Breath Test Uncertainty Data
After a long struggle the Minnesota Bureau of Criminal Apprehension (BCA) finally released the uncertainty of measurement data for the breath testing machines used in DWIs. So how inaccurate are breath test results? A BCA Scientist admitted that it could be as high as ± .01 at the .08 BAC level – Meaning a result at .08 BAC could actually be as low as .07 BAC or as high as a .09 BAC. This data shows that breaths tests are over 3X more inaccurate than blood tests. The uncertainty of measurement increases at the .16 BAC level or higher, suggesting a margin of almost double than that at the .08 level.
Two recent Minnesota court decisions favored scientifically-backed data and ruled in favor of the defense in challenges to the test’s accuracy. The first is Janssen v. Commissioner of Public Safety, a court of appeals decision. The second was a Ramsey County district court decision. Both issues arising at the civil implied-consent hearing.
Janssen v. Commissioner of Public Safety
Minnesota Statute Section 169A.53, subd. 3(b)(8)(i) (2015), only provides that whether a driver’s alcohol concentration was 0.08 or more at the time of testing is within the scope of an implied-consent hearing. So, essentially, the issue was whether the district court was precluded from considering the accuracy of a breath test at or above the .16 BAC level also. The Court held that it is not and a driver may challenge the accuracy of a .16 BAC result at the implied consent hearing.
This is important for a number of reasons. The most important of which is the fact that a driver with a .16 BAC (twice the legal limit) may face increased criminal penalties. The driver will also face extended license revocation (one-year, as opposed to up to 90-days for a BAC under .16) and/or license plate impoundment.
Ramsey County District Court
This was another civil-implied-consent hearing. The Petitioner (driver) challenged the accuracy of the breath testing machine after his two breath samples yielded .173 and .168 BAC results. The Petitioner called an expert witness to testify that the breath testing machines do not test for uncertainty of measurement and therefore it is impossible to determine the accuracy or reliability of the measurement. The Court agreed and rescinded his one-year license revocation based on the fact that the State could not prove his BAC was actually over .16.
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