Joliet, Illinois (CNN) -- The murder trial of former Illinois police officer Drew Peterson will be postponed while prosecutors appeal a judge's ruling that keeps some witness statements out of court as hearsay, the state's attorney announced Wednesday.
Jury selection had been set to begin Thursday in Joliet, south of Chicago, but the appeal is likely to push back the start of the trial for weeks and perhaps months, said Will County State's Attorney James Glasgow.
"The people of the state of Illinois are entitled to a fair trial, and I intend to see that they get one," Glasgow said in a statement issued by his office Wednesday afternoon. "As state's attorney, I am obligated to appeal the judge's ruling to ensure that every legally admissible statement may be presented at trial."
Peterson has pleaded not guilty to first-degree murder in the 2004 death of his third wife, Kathleen Savio. Defense attorney Joel Brodsky told reporters the state's appeal is a tacit admission that "they don't have a case" without hearsay.
Peterson has been jailed for more than a year, and Brodsky said he will seek his immediate release now that the trial has been pushed back.
Circuit Judge Stephen White ruled Tuesday that he would not reconsider an earlier ruling that barred prosecutors from presenting a list of statements they had sought to use in their case. Glasgow argued that the judge should reverse that ruling because of a recent Illinois Supreme Court ruling, and he has asked a state appeals court to overturn White's order upholding his earlier decision.
White has kept details of the statements under wraps to keep them from potential jurors, who will be drawn from a pool of 240 people once proceedings begin.
Savio's death initially was ruled an accidental drowning, but her body was exhumed and re-examined in 2007 after the still-unsolved disappearance of Peterson's fourth wife, Stacy. The onetime Bolingbrook, Illinois, police sergeant denies any wrongdoing in either case.
In Session Correspondent Beth Karas contributed to this report.