Savio's body was exhumed late last year after he 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 he 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.
Peterson told the (Joliet) Herald-News that the ruling in Savio's death shocked him. "You're kidding me. Unbelievable. That's hard to believe," he told the newspaper.
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.
Peterson's attorney did not immediately return a telephone call Thursday from The Associated Press.
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." her 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.
Peterson's 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.
