Kathleen Savio died by drowning and her death was ruled a homicide, Dr. Larry W. Blum said in an autopsy report released Thursday by the state's attorney's office. It was the second autopsy performed on Savio.
She was found dead in her bathtub in March 2004, shortly before her divorce with Drew Peterson was finalized. Four years ago, a coroner's jury ruled her death was an accident.
Savio's body was exhumed late last year after Peterson was named a person of interest in the disappearance of his fourth wife, Stacy. He has said Stacy Peterson ran off with another man, but her relatives deny any affair and say she would not have willingly left her two young children.
"We have been investigating this as a murder since reopening the case in November of last year," Will County State's Attorney James Glasgow said. "We now have a scientific basis to formally and publicly classify it as such."
Peterson, 54, has denied any involvement in either case and has not been charged with wrongdoing. He was a sergeant and 29-year veteran in the Bolingbrook, Ill., police department when he resigned after coming under suspicion in Stacy Peterson's disappearance.
"There's still nothing that points to Drew," Peterson's attorney, Joel Brodsky, told CBS' The Early Show. Asked how his client was handling the homicide ruling, Brodsky said of Peterson, "He is still very upbeat and very confident. He knows he didn't do anything wrong."
Peterson told the (Joliet) Herald-News the ruling in Savio's death shocked him. "You're kidding me. Unbelievable. That's hard to believe," he told the newspaper.
Savio's family members said Thursday they always believed she had been killed and the confirmation was welcome. "But it could have prevented if people would have listened to her before she was killed," niece Melissa Doman said.
Savio, 40, had filed an order of protection in 2002 after Peterson allegedly knocked her down, ripped off a necklace and left marks on her body. She wrote in the order that she feared Peterson could kill her.
Doman declined to say who she thought was responsible for Savio's death. She said she did not want to interfere with any current investigations or leads that authorities may have.
Authorities are not prepared to name a suspect in Savio's death, but police and a grand jury are actively investigating both cases, said Charles Pelkie, a spokesman for Glasgow's office.
His second wife, Vicki Connolly, has said that during their marriage, an increasingly controlling Peterson hit her and told her he could kill her and make it look like an accident.
Connolly said police sometimes came to the house when the couple were having problems, but she said the officers were friends of theirs and no reports ever were filed.
Peterson's first two marriages ended in divorce.