CHICAGO (CBS) — The pathologist who ruled Kathleen Savio was the victim of a homicide after authorities reopened their investigation into her death said being skeptical was the key to determining it was no simple accident.

CBS 2’s Mike Puccinelli reports Dr. Larry Blum’s testimony at Drew Peterson’s murder trial this summer was a key factor in the jury’s decision to convict Peterson of killing his third wife.

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Blum performed the second autopsy on Savio’s body, three and a half years after a coroner’s jury determined her 2004 death to be an accident.

His autopsy ruled Savio’s death was a homicide. On the last page of his report, Blum wrote, “The cause of the death of Kathleen Savio was drowning. The manner of the death was homicide.”

It was those words from Blum’s autopsy report that, perhaps more than any others, sealed the fate of Drew Peterson.

“It’s always gratifying to know that the jury has heard and understood what you’re telling them,” Blum said.

Despite the passage of time and the decomposed state of Savio’s body, Blum was able to determine that Savio’s injuries were consistent with murder. He pointed to injuries to both the front and back of her head and body.

“[A] fall to the back in the tub would produce injuries to the back, not to the front,” he said.

Those weren’t the only injuries that Blum said weren’t consistent with a slip and fall.

“The hemorrhage in the chest muscles, which indicated a forceful drowning over the sink, over the toilet, [or] over the bathtub,” he said.

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However, during the first autopsy, the original pathologist in the case determined the injury pattern could have been caused by an accidental fall.

Blum said such a statement was unusual, because that doctor wasn’t asked to rule on the manner of death. Blum said the original pathologist likely was pressured into ruling Savio’s death was an accident.

“I don’t believe he put it in there on his own. I think he was asked to make a statement,” Blum said.

He said the initial investigators appeared to do their work with blinders on, and he said contradicting the initial Illinois State Police investigation wasn’t easy.

“There were many things, many red flags that should go up in this case,” Blum said. “They were down.”

But he said, in the end, it was Savio who won her case. He said he feels he was able to be a voice for her.

“I’m only the go-between, so to speak; but it’s her injuries, her circumstances, her scene that all spoke, and spoke very loudly to that jury,” he said.

Asked if he believed that, if the initial investigation had been done more thoroughly that perhaps Drew’s missing fourth wife, Stacy Peterson, would still be around, Blum said that’s absolutely possible.

Drew Peterson has been named a “person of interest” in Stacy’s disappearance, but has not been charged in that case. After Peterson was convicted of Savio’s murder, Will County State’s Attorney James Glasgow said “We are going to aggressively review that case with an eye towards potentially charging it.”

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Authorities believe Stacy is dead, but Drew Peterson has maintained she is alive, and that she ran off to start a new life with another man.