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ST. LOUIS – The St. Louis-based company Intoximeters, which makes breathalyzers used by police and prosecutors to convict drunk drivers, is at the center of a controversy regarding the reliability of its machines in Michigan.

According to attorneys and legal experts, the controversy could derail drunk driving cases there.

Michigan State Police sent a letter to its law enforcement partners in that state, alerting them to the concerns.

The letter cites “performance-related issues” and drunk driving cases that could “impacted by contractor errors.”

It does not specify the errors or how many cases may be impacted. The letter says Michigan State Police are responsible for the purchase, certification, and maintenance of the machines at law enforcement agencies across the state. Michigan state police had contracted with the company to calibrate and service its devices.

203 of Datamaster DMT machines have been taken out of service until proper calibration can be verified. Michigan State Police will keep using the devices but now calibrate them, themselves.

No one from Intoximeters would comment to Fox2/News 11 on Wednesday.

Police and prosecutors rely on the machines to be precise.

In most states, a blood alcohol content (BAC) registered by a breathalyzer (BAC) of .08 is legally drunk; a BAC of just a fraction lower, .07 for instance, is legal.

“We really can’t rely on the testimony of the person who did it (the breathalyzer test) anymore if in fact they’re found to have been fraudulent,” said Michigan DUI defense attorney Ed Sternisha. “My big concern is what about those who already pled guilty based on that. What are we going to do? Even if we can overturn a conviction, you can never give anyone back the time they served.”

So far, we’ve confirmed multiple police agencies in the St. Louis area use Intoximeters devices. So far, all who’ve responded say trained police officers calibrate the machines, not workers hired by Intoximeters. The calibration is required every 35 days in Missouri.

Police do say they may call on the company for help if the machines malfunction.