But Judge Nicholas McNamara ruled prosecutors can still use blood drawn from Bruce Burnside after the crash.
The Wisconsin State Journal reports McNamara found the officer who gave the sobriety tests to Burnside did not have a reasonable suspicion that Burnside had been drinking.
Defense attorney John Hyland says he might appeal the decision. But because Burnside's trial is scheduled to begin May 12, Hyland didn't know whether the court would accept an appeal.
Burnside is charged in the April 7, 2013, death of Maureen Mengelt.
Burnside is no longer employed by the South-Central Synod of Wisconsin of the Evangelical Lutheran Church in America.