(CNN) -- Prosecutors have won a step in the legal battle that has delayed Drew Peterson's murder trial, with a court ruling Wednesday that could have a profound effect on the proceedings.
The Illinois Supreme Court told an appellate court to reconsider whether eight hearsay statements previously ruled inadmissible should be admitted after all.
Peterson, a former police sergeant from Bolingbrook, Illinois, is accused of killing his third wife, Kathleen Savio, in 2004 and remains under investigation in the October 2007 disappearance of his fourth wife, Stacy Peterson.
Peterson maintains he is innocent.
Prosecutors have built a case against Peterson largely based on pathology reports and 14 hearsay statements by Savio and Stacy Peterson to family and friends that claim Drew Peterson was combative and threatening.
Will County Circuit Court Judge Stephen D. White ruled that eight of the 14 statements were inadmissible for trial.
Just before Peterson's trial was to begin in July 2010, Will County prosecutors appealed that ruling. The trial was delayed.
In July, the Illinois Appellate Court dismissed the appeal, saying it lacked jurisdiction to weigh in because prosecutors had missed a deadline to file the appeal.
On Wednesday, the Illinois Supreme Court ordered the appellate court to "address the appeal on the merits."
Will County State's Attorney James Glasgow said he was "extraordinarily pleased" and looks forward to the appellate court's ruling.
" We anticipate a trial sometime in the spring," Glasgow said in a statement.
Peterson attorney Steve Greenberg told CNN, "We're disappointed because it delays having a jury hear what they (the prosecutors) actually have, which isn't much. And it means that someone stays in jail while the prosecutors go along to try and put together a case."
When Savio was found dead n 2004, her death was ruled accidental.
In October 2007, after Drew Peterson's fourth wife Stacy went missing, he became the focus of a police investigation. Authorities exhumed Savio's body and conducted a second autopsy, this time ruling her death a homicide.
Since Savio is dead and Stacy Peterson is missing, the defense argues that using their alleged statements to family and friends violates Peterson's Sixth Amendment right to confront the witnesses against him.
In general, hearsay statements made to third parties cannot be introduced at trial unless a defendant can cross-examine the person who made them. There are some exceptions if prosecutors can prove the statement is reliable. But a new Illinois law, which some call "Drew's Law," goes beyond those exceptions.
The law, passed while investigators were looking for Stacy Peterson in 2008, allows courts to consider statements from "unavailable witnesses," provided prosecutors can prove the witness was killed to prevent his or her testimony.
More than 70 witnesses testified early last year at the Peterson hearsay hearing.
CNN's Josh Levs and Mayra Cuevas contributed to this report.