The Wisconsin Department of Justice could challenge a federal judge’s decision to overturn an operating while intoxicated conviction, which could potentially jeopardize OWI convictions across the state.

State attorney Marguerite Moeller asked a federal judge to reconsider a decision to drop an OWI conviction based on breathalyzer results.

U.S. Magistrate Aaron Goodstein of the U.S. District Court in Milwaukee ruled Richard Fischer’s 2007 OWI conviction was a violation of his rights and granted Fischer’s request for a writ of habeas corpus. As a result, Fisher’s conviction was overturned.

Fischer was arrested for operating a motor vehicle while intoxicated in January of 2005 in Ozaukee County after drifting in and out of lanes and performing poorly on field sobriety tests, according to police reports.

When police administered a Preliminary Breath Test, Fischer recorded a breath alcohol content of .11 percent. A blood test conducted less than an hour later showed Fischer had a blood alcohol content of .147 percent, according to the court ruling.

Fischer’s attorney James Shellow argued the increase in Fischer’s blood alcohol level showed he was not over the legal limit at the time he was driving. Shellow called an expert who utilized a “curve argument” to show how Fischer could have been under the legal .08 limit at the time he was arrested. The argument suggests while someone’s intoxication level may have been rising at the time of arrest, he was still under the legal limit.

Once Fischer was blood tested at the hospital, his alcohol content was higher than when he was actually driving the car, according to the expert, but the expert based his argument on Fischer’s breath test, which is not admissible at trial.

According to Wisconsin State Law, breath tests cannot be used at trial to prove guilt, but they can be used by police to show probable cause for an arrest.

Allowing experts to testify on PBT results at trials could allow defense attorneys to make a similar “curve argument” and could lead to a decrease in convictions, according to Nina Emerson, the Director of the Resource Center for Impaired Driving at the University of Wisconsin.

In Fischer’s appeal to the Wisconsin Supreme Court, the court reaffirmed that breath tests were not admissible.

“Such testimony would only confuse rather than assist the jury,” said Justice Annette Ziegler, concurring with the majority opinion.

The problem with breath tests is that the machines in police cars are unreliable and are not as accurate as machines in hospitals and police stations, according to Emerson.

Emerson said the tests used by police are meant to give the officer a general idea of the subject’s blood alcohol level.

If Goodstein’s decision is not reversed, it could have a significant effect on future OWI cases in Wisconsin, a state with over 44,000 drunken driving convictions in 2009, according to the Department of Transportation.

However, Emerson points out prosecutors could also use breath tests in a similar fashion to show guilt.

Prosecutors could claim if the blood test was lower than the breath test, then the driver’s alcohol level should have been higher at the time they were driving.

“Be careful what you wish for,” Emerson said. “If you open that door, prosecutors could use it.”