Drew Peterson is a suspect in his fourth wife's disappearance and has been questioned about the murder of his third wife.

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Drew Peterson's attorney says the trial should last about a month

Peterson is charged in the 2004 death of Kathleen Savio, his third wife

In April, an Illinois appellate court ruled hearsay evidence may be used against Peterson

CNN  — 

Jury selection began Monday in the murder trial of former Chicago-area police officer Drew Peterson, who is accused of killing his third wife and is the leading suspect in the disappearance of his fourth.

Opening statements are scheduled for next week. Peterson’s attorney Joel Brodsky told CNN’s sister network In Session that he expects the trial to last about a month.

Peterson, 58, is charged in the 2004 death of his third wife, Kathleen Savio. He also remains under investigation in the October 2007 disappearance of fourth wife, Stacy Peterson.

In April, an Illinois appellate court ruled that prosecutors may use potentially incriminating statements made by Savio and Peterson’s still-missing wife against him – a key development in the case.

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The ruling overturned an earlier judge’s decision that forbid prosecutors from using eight statements made by Savio before her death and by Stacy Peterson before her disappearance.

When Savio was found dead in a bathtub in 2004, it was ruled accidental. She had been divorced from Peterson for about five months when she died, though a court was still deciding how their marital assets would be divided. Savio was to receive part of Peterson’s pension and other support.

Just eight days after his divorce from Savio, Peterson married Stacy Cales, then 19.

After Stacy Peterson went missing in October 2007, her husband 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 has argued that using their alleged statements to family and friends violates Peterson’s Sixth Amendment right to confront the witnesses against him.

Among the statements the appeal court allowed is one in which Stacy told her pastor that she saw Drew Peterson return home the morning Savio died, dressed in black and carrying a bag of women’s clothes that were not hers.

Drew Peterson goes on trial in 3rd wife’s death; 4th wife still missing

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 in 2008 while investigators were looking for Stacy Peterson, allows courts to consider statements from “unavailable witnesses,” provided prosecutors can prove the witness was killed to prevent his or her testimony.

The intrigue surrounding the case has added to Drew Peterson’s mystique and prompted the Lifetime movie “Drew Peterson: Untouchable,” which set a ratings record of 5.8 million viewers for the channel when it premiered in January.

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In Session’s Michael Christian contributed to this report.