A forensic pathologist told FOX News' Greta Van Susteren his examination of the exhumed body of a police officer's wife shows her death was a homicide.

"It is my opinion to a reasonable degree of medical certainty ... that it is a homicide," former New York City chief medical examiner Michael Baden said. "That is what I would have put on the death certificate."

The ruling concerning the death of Kathleen Savio, the third wife of former Illinois police officer Drew Peterson, contradicts a 2004 decision by a coroner's jury that Savio, whose body was found in a bathtub, died of an accidental drowning.

Peterson has been named a suspect in the disappearance of his fourth wife, Stacy Peterson, who disappeared on Oct. 28.

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He said there was enough evidence to initially suspect she was a homicide victim because she was an adult, healthy and hadn't been drinking when she was found in the tub.

"Even then there was evidence of multiple blunt force traumas," Baden said.

Click here to view the MyFOXChicago.com video report on the case.

Baden said signs of struggle including bruises on the hands, chest and abdomen still were fresh with purple discoloration but there were no fractures. Although there were no bruises on her arms, Baden believes she may have drowned by having her head pressed under water.

"I don't think there is any possibility this was an accident," he said. "I don't think there is any evidence this was a suicide."

Baden told FOX News the 2004 jury might not have seen all the evidence related to the case at the time of the verdict.

Baden said Savio's family was suspicious of the death because she had been wearing jewelry and her hairstyle was different than her normal pattern when bathing and they had not heard from her in the 36 hours before the incident.

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"She was beat up and placed in the bathtub as a cover-up for whoever done this," Sue Savio Doman, Savio's sister, told a FOX affiliate.

A coroner's jury initially ruled that Savio's 2004 death was an accidental drowning. But now, with Drew Peterson's fourth wife missing for more than two weeks, authorities are re-examining the circumstances of Savio's death.

Click here to read Jamie Colby's blog: "Inside Drew Peterson's House."

"There was marks on her hips, her arms, her elbows, on her legs, her feet. ... There was a struggle. She did fight," Savio Doman said.

Peterson, 53, who resigned this week as a Bolingbrook police sergeant, has not been named a suspect in Savio's death, but he is a suspect in the disappearance of his fourth and current wife, Stacy, who last was seen Oct. 28 and whose case authorities have called a possible homicide.

Click here to read the report from America's Most Wanted.

Drew Peterson has an unlisted number. He has denied any involvement in either case and said he believes his 23-year-old wife left him for another man and is alive.

Savio's body was exhumed this week at the request of Will County State's Attorney James Glasgow, who has said after examining evidence he believes her death was a homicide staged to look like an accident.

The state's attorney's office allowed Baden to use the county morgue for his work and a state's attorney's investigator attended the autopsy, spokesman Charles Pelkie said.

The results of Will County's official autopsy will not be available for days, authorities said.

Savio's brother, Nick Savio, told WFLD-TV that Baden's report, which Pelkie said would be reviewed by investigators, was a step forward.

"It gives us a little bit of closure ... but we're still far, far, far away from getting the closure that we really do need, and that is if whoever is responsible for this, that person should be put behind bars and justice hopefully will prevail this time for the Savio family."

Steve Carcerano, who says he was there when his friend Drew Peterson first saw Savio's body in the tub, said he was called by a grand jury looking into Savio's death and is to testify next week.

When Peterson saw the body, he was obviously surprised and distraught, Carcerano said.

"He checked her pulse right away to see if she was dead or alive. Then he was, 'Oh, my God, what am I gonna tell my kids? What am I gonna tell my kids?"' Carcerano said.

Documents released by Savio's family show she had accused Peterson of stealing her car while she was in church with one of her children. According to one letter the family said was sent to Will County prosecutors in November 2002, she also accused Peterson of beating her a number of times so severely she "ended up in the emergency room."

She also described in the letter a time she believed he would kill her: "He pulled out his knife that he kept around his leg and brought it to my neck."

Pelkie said it remains unclear if that letter ever came to the office. He said it was not in the files Glasgow read when he began reinvestigating Savio's drowning.

But many allegations in the letter are consistent with those Savio made in an order of protection filed against Drew Peterson in 2002, as well as accounts given by her family members.

Carcerano said he never saw Peterson strike or shout at his wife in anger, though he said he saw Savio attack Peterson.

"I've seen her slap him in the face right in front of me, seen her spit in his face and chasing him around with an extension cord, hitting him with it," Carcerano said.

Attorney Fred Morelli, who once represented Peterson, said he never heard the knife claims about his former client.

"That's the first I've heard of that," Morelli said. "That's crazy. ... (Peterson) was a very pleasant, personable fellow. Other than that, I don't know."

The Associated Press contributed to this report.