Reliability of DWI testing being challenged in Minnesota

- Like the scale in your bathroom, breathalyzers aren't perfect, but unlike your scale, the breathalyzer can send you to jail. In hearings in Ramsey and Hennepin Counties, attorneys are challenging how the state crunches numbers that come from breath machines.

“We've learned that the Minnesota Crime Lab is hiding the ball. Essentially, they aren't reporting the true values of these tests. And they're misrepresenting the test results. A .08 may not be a .08,” said Chuck Ramsay, a defense attorney at the Ramsay Law Firm, who is challenging the reliability of the tests.

The Ramsay Law Firm brought in Dr. Janine Arvizu, a chemist specializing in measurement quality, and was featured in Netflix’s “Making a Murderer.” In the hearing, Ramsay asked her “whether or not the breath test results are scientifically valid and reliable?” Dr. Arvizu answered, “they are not.”

The concerns are over two statistics concepts known as bias and uncertainty of measurement. Explaining bias, Ramsay said the state averages the biases of the entire fleet of machines — rather than applying the bias of each individual machine. 

“Let’s say we have two bathroom scales. My bathroom scale, of course, is reading high. And yours, which is probably reading a bit too low. If mine is showing it’s five pounds too heavy, and yours is showing it’s five pounds too light, together, if you average the bias of the two, it will be a zero. And it will give the false impression that both scales are perfect when individually they’re not,” Ramsay told Fox 9.

Ramsay, a designated a Forensic Lawyer Scientist by the American Chemical Society, also criticizes the state for not reporting the uncertainty of each machine.

“After the state adjusts for bias, they have to calculate the uncertainty of the measurement for the breath test. The state already does this for blood and urine tests, but they refuse to do it for breath tests,” Ramsay said.

Minnesota is in the majority of states that do not provide the uncertainty of measurement, but Ramsay says there is a growing number of states providing the information. And he pointed to the International Organization of Standardization writing that without “information on uncertainty, there is a risk of misinterpretation of results.” 

“Not only are innocent people right now being convicted of being over .08 when they're not, but guilty people who are over .08 are going undetected because this breath test machine may indicate they're under the legal limit when they're actually over,” Ramsay told Fox 9.

A judge could rule on issues related to the challenging of the numbers within the next few months.

The Bureau of Criminal Apprehension provided a statement to Fox 9 saying: “We cannot comment regarding an ongoing court case. However, the devices provide accurate results and we welcome the opportunity to address any challenges in court.”


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