Felony gun charges were dismissed Thursday during the court appearance of a former Bolingbrook police sergeant suspected in his wife's disappearance.
Drew Peterson was accused of possessing an assault rifle with a barrel shorter than allowed by state law.
Judge Richard Schoenstedt ruled after the Will County state's attorney's office refused to comply with a his order to turn over all documents compiled that lead to its decision to arrest Peterson on the gun charges.
Peterson's attorney, Joel Brodsky, alleged that authorities were vindictively prosecuting Peterson because he was successful in winning court orders they'd fought. One of those compelled them to give Peterson's guns to his adult son.
The judge considered holding prosecutors in contempt of court before finally deciding to dismiss the case, NBC5's Anthony Ponce reported.
"Obviously, we're very pleased," Brodsky said. "We believe that the only real reason that the state would have not wanted to turn over the documents is because they would have helped us. Otherwise, if they would have been of no help, I'm assuming they would have gladly turned them over."
Chuck Pelkie, a spokesman for the Will County State's Attorney, said prosecutors planned to appeal to the state's Third District Court of Appeals.
"This as another step in the process," Pelkie said. "We plan to prevail on appeal. This is another step in the process for us."
Peterson hasn't been charged in the 2007 disappearance of Stacy Peterson and insists that his 23-year-old wife voluntarily left him for another man.
The death of his third wife is also under investigation after authorities exhumed her body, conducted a second autopsy and labeled her bathtub drowning a homicide after it was initially ruled an accident.