July 29, 2012 -- The murder trial of former Illinois cop Drew Peterson could hinge on the statements of two women who won't be at that trial: his third wife he is accused of murdering and his fourth wife who has disappeared.
A jury of seven men and five women will hear opening arguments Tuesday on whether Peterson, 58, killed his then-wife Kathleen Savio in 2004 and made it look like an accident.
Peterson skyrocketed to notoriety in 2007 when his fourth wife, Stacy Peterson, disappeared. Cops exhumed Savio's body as part of their investigation into Stacy's disappearance, eventually changing the cause of Savio's death from an accident to homicide and charging Peterson with murder.
Stacy has never been found, and the case has garnered widespread media attention focused on Peterson, whose story was made into a Lifetime movie, with Rob Lowe playing Peterson, earlier this year.
In the trial, prosecutors will argue that bruises on Savio's neck, together with Peterson's history of domestic violence and his statements about Savio's death to his fourth wife prove that he murdered Savio.
Drew Peterson Case To Focus on Wives' Statements
Peterson, who was a sergeant in the Bolingbrook, Ill., police department, was in the middle of a bitter divorce from Savio and had already begun seeing Stacy Peterson at the time of Savio's death.
Kathleen Zellner, a Chicago attorney who has been following the case, noted that the prosecution is expected to try and use statements that Stacy Peterson made to her minister before her disappearance, in which she said that Peterson had admitted to killing Savio. If the judge admits the hearsay statements of Stacy Peterson, the testimony could be damaging to Peterson, she said.
"What the judge is going to do is he's going to wait and make individual rulings each time the prosecution tries to introduce hearsay, not give a blanket ruling, but listen to see if they open the door in some way that makes the hearsay admissible. He'll make this a day by day ruling on these different pieces," Zellner said.
"Essentially we've got Peterson confessing the murder of Savio to his fourth wife, but we still have the question of whether that will come in," Zellner said.
Prosecutors will also try to admit Stacy Peterson's statements to her minister that she saw Drew Peterson arrive home with women's clothing around the time of Savio's death.
Savio's sister may take the stand to describe Savio's statements that Peterson threatened her with a knife and said he could make her death look like an accident.
"That doesn't concern us," Peterson's attorney, Joel Brodsky told ABC News earlier this week. "Anybody that knows anybody that has been through a divorce knows that people say things and do things that is totally out of character, and clearly Kathy was trying to build a case to try and get as much money as she could."
The trial may also hang on which death investigator is more believable to the Joliet, Ill., jury. Forensic pathologist Bryan Mitchell, who investigated the death in 2004 and ruled that a gash on Savio's head and abrasions on her body were consistent with an accidental fall, died earlier this year before he could testify at trial. The defense will likely call expert witnesses to testify that her death was an accident.
Drew Peterson's Murder Trial Begins Monday
Larry Blum, who investigated Savio's body after it was exhumed in 2007, will testify for the prosecution at the trial about what made him switch the cause of death from an accidental fall to homicidal drowning.
"First, they are not going to be able to say that (the death investigation was botched) because it wasn't," Peterson's attorney, Brodsky said. "By saying that if they had done a better job in the investigation, then they would have been able to prosecute Drew Peterson, that lowers the burden of proof. Where you don't have evidence, you presume innocence."
Savio's body was discovered in her bathtub by neighbors after Drew Peterson arrived at her home one Monday morning to drop their children back off after a weekend in his custody. When Savio did not answer the door, he asked neighbors to check on her. They found her dead in the second floor bathroom and. Peterson then rushed upstairs to take her pulse.
Peterson's legal team told ABC News that there is no forensic evidence tying Peterson to Savio's murder, and that the prosecution should not have pursued the case against Peterson.
"We have always said, and this has never changed: They simply don't have any evidence. They have conjecture, rumor, speculation, hearsay, but they don't have any evidence. Even a predispositioned jury is going to want to hear evidence, and they don't have any," Brodsky said.
Peterson's son, who was with him during the weekend in question, may also be called to testify for his father about his father's whereabouts the weekend of Savio's death.