JOLIET | |Authorities probing the disappearance of a police officer's wife said Friday he is now considered a suspect in a potential homicide investigation, and that the death of an ex-wife three years ago appeared to have been staged as an accidental drowning.

Authorities received court approval to exhume the body of an ex-wife of Bolingbrook Sgt. Drew Peterson as they continued the search for his wife, Stacy, who was last seen Oct. 28.

Illinois State Police Capt. Carl Dobrich said Peterson, 53, has moved from being a person of interest in the disappearance of his 23-year-old wife to "clearly being a suspect."

Dobrich also said the case was now a potential homicide investigation.

"We have mixed emotions right now," said Pamela Bosco, Stacy Peterson's adoptive stepmother. "We're sad, but we needed to move on, and this is something we've needed to hear for a long time."

Peterson has said Stacy Peterson phoned him and told him she had left him, and Peterson believed it was for another man. His attorney, Fred Morelli, did not immediately return calls seeking comment.

Stacy Peterson was studying nursing at a junior college near where the couple lived in the Chicago suburbs. Her family has said she feared her husband, was making plans to divorce him and would not have willingly left her children, ages 2 and 4.

A coroner's jury ruled the 2004 death of Kathleen Savio, Peterson's third wife, an accident, even though there was no water in the bathtub where the 40-year-old's body was found face-down, her hair soaked in blood from a head wound. Investigators theorized the water had drained.

But in a petition the Will County state's attorney filed Friday listing the reasons authorities wanted to exhume Savio's body, prosecutors said a review of evidence in the case "is consistent with the 'staging' of an accident to conceal a homicide."

Prosecutors said they reviewed photographs of the crime scene and autopsy, the autopsy protocol, and police reports.

They determined the blood evidence wasn't consistent with water slowly leaking out of the tub, that the one-inch gash on the back of Savio's head was not sufficient to render her unconscious, and that abrasions on her body weren't consistent with falling on a smooth surface like a bathtub, State's Attorney James Glasgow said.

"With 29 years of experience, there's no doubt in my mind it wasn't an accident," Glasgow said.

Glasgow, who took office more than nine months after Savio's death, also said he reviewed records that indicated Savio had sought a domestic violence complaint against her husband.

Peterson was never charged, but Savio was twice charged in 2002 with battery and domestic battery, Glasgow said. She was found not guilty both times.

"Twice Drew Peterson was able to convince the state's attorney's office to bring charges against his wife, but she was never able to do the same," Glasgow said.

Jeff Tomczak -- the state's attorney when domestic violence charges were filed against Savio and when she died -- did not return a call for comment to his law firm.

Will County Circuit Court Judge Daniel J. Rozak signed the petition granting the exhumation of Savio's body Friday. Authorities would not say when the body would be exhumed.

Also Friday, the Bolingbrook Police Department announced that Peterson has been relieved of duty and placed on suspension without pay pending completion of an internal affairs investigation and hearing.