( 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 . Ex-cop attends hearing in wife 's death . 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 can not 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 . Peterson finds Lifetime movie `` laughable '' Peterson 's attorney : Drew will get first class defense . Get a glimpse of Drew Peterson 's home . In Session 's Michael Christian contributed to this report .
Drew Peterson 's attorney says the trial should last about a month . The defense is expected to call more than 100 witnesses and present evidence that will be used against them in their closing arguments on Monday. In April , an Illinois appellate court ruled hearsay evidence may be used against Peterson .