Will County prosecutors want jurors to hear several hearsay statements they say link the former Bolingbrook police officer to the 2004 drowning of his third wife. A state appellate court ruled the statements were not admissible and Glasgow's office announced an appeal on Friday.
"We are prepared to go to trial regardless of the outcome, but I've got an obligation as the prosecutor for this jurisdiction to do everything I can within the law to bring the best case possible in the prosecution. And that's what we're doing here with this appeal," said Glasgow.
The appeal was widely expected because the hearsay evidence is considered crucial in a case in which prosecutors have not revealed physical evidence linking Peterson to ex-wife Kathleen Savio's death.
Glasgow says a trial won't happen until sometime next year.
Joel Brodsky, Peterson's attorney, says the ruling is just stalling the evitable.
"Drew Peterson has been locked up well over two years in isolation without a right to a speedy trial and this drags it out even further," he said.
No decision has been made to allow the evidence. Peterson is jailed on $20 million bond and his attorney plans to petition to court to allow him to go free while they make the decision.
Peterson is suspected in the 2007 disappearance of his fourth wife, Stacy Peterson, but he hasn't been charged.
The Associated Press contributed to this report.