Joliet, Illinois (CNN) -- The trial of former Chicago-area police Sgt. Drew Peterson, accused of killing his ex-wife, focused Wednesday on an incident in which he allegedly had threatened to kill her with a knife.
Defense attorneys sought to discredit Kathleen Savio's account of the July 2002 incident, in which she had said Peterson pushed her down the stairs of her home, upset about their divorce proceedings, and told her to turn her head so he could kill her.
Peterson, 58, is on trial, charged with the murder of Savio, his third wife, who was found dead in her dry, clean bathtub March 1, 2004.
The case did not arise until after Peterson's fourth wife, Stacy, went missing in October 2007. It was during the search for Stacy Peterson, who has never been found, that investigators said they would look again at Savio's death, which was initially ruled a drowning.
Savio's death was ruled a homicide in February 2008, and Peterson was later arrested and indicted on first-degree murder. The court heard Wednesday afternoon from the forensic pathologist who conducted the second autopsy that led to the homicide ruling.
Peterson has been called a suspect in Stacy Peterson's disappearance, though he has never been charged in that case.
Wednesday morning's testimony began with the cross-examination of Bolingbrook, Illinois, Police Lt. Teresa Kernc, who took a police report from Savio about the alleged knife incident in 2002. Prosecutors examined Kernc on Tuesday.
Savio had written in the police report that Peterson pushed her down the stairs and told her not to get up, then told her how "awful and bitchy" she was and that she should stop being so terrible to him.
Savio had written that she grew tired of his rant, so she told him, "'Go ahead, just kill me.' He said, 'Where do you want it?' and I said, 'In the head.' He said, 'OK, then turn your head,' and I did it. And then he said that he would never be able to hurt me. And then he left."
Kernc testified that Savio told her verbally that Peterson threatened her with a knife, but that she didn't include it when she wrote her statement.
"I told her to put in the report what happened. I said, 'The knife part isn't in here. You need to put in here what actually happened,'" Kernc testified. "Then she wrote it in there, and a short time later she crossed the knife part out. She expressed concern about him being arrested and losing his job."
Defense attorney Steve Greenberg noted the incident is alleged to have happened July 5, 2002, but that Savio didn't call Kernc to make the report until July 18. He also pointed out that Peterson had served Savio with a criminal complaint just "10 or 15 minutes" before she filed the police report, but that she never mentioned that to Kernc.
Savio had told Kernc that after Peterson left she immediately called several people, including friend and neighbor Mary Pontarelli, and told them about the knife incident. But according to Greenberg, Pontarelli said Savio described only a "nice conversation" with her husband.
That description was "consistent" with what Peterson told Kernc when she interviewed him about the incident, Greenberg said.
Kernc ended her testimony by saying she wasn't sure whether Savio was telling the truth about Peterson wielding a knife.
"You had some concerns about whether that actually happened?" Greenberg asked.
"Yes," Kernc replied.
"And that was based on your complete investigation?" he asked.
"Yes," Kernc said.
The afternoon session of the trial was expected to include testimony by the doctor who performed Savio's second autopsy, and by Scott Rossetto, Stacy Peterson's friend.
In the afternoon, the court heard from Dr. Larry Blum, who performed the autopsy on Salvio's body after she was exhumed in 2007.
Blum testified that Savio suffered a laceration to the back of her scalp, which led to dried blood on her face and around the drain when she was found. He said it would have been "impossible" for the blood to have dried like that had there been water in the tub.
He also testified that Salvio had a number of fresh bruises -- less than an hour old -- on the front of her body, including to her hip bones, thigh, shins, and hands.
Blum said he also found a fresh abrasion on her buttocks that "would not be consistent with someone's slip and fall."
He did not testify about why the first autopsy would have ruled her death accidental.
The Peterson trial began July 31 and is expected to last about four weeks.
Repeated missteps by the prosecution are angering Judge Edward Burmila and the defense. At least four times since the trial began, prosecutors have allowed witnesses to testify to details Burmila has told them not to go into -- such as whether Savio had a protective order against her husband or allowing Blum to demonstrate climbing into the bathtub.
In some cases the defense has sought a mistrial and in others they have asked the judge to strike entire testimony. Burmila has instead ordered the jury to disregard elements of the testimony that went against his orders.
"The disrespect to the court is shocking," Burmila told the prosecution Wednesday.
Peterson was married to Savio in 2001 when he had an affair with then-17-year-old Stacy Cales, whom he would later marry. Savio and Peterson filed for divorce in October 2001 and their relationship remained contentious for the next several years.
Bolingbrook police records indicate officers were called to Savio's home 18 times to intervene in domestic fights from 2002 to 2004. Peterson had Savio arrested twice for domestic violence, though she was found not guilty in both cases.
On February 27, 2004, Peterson picked up his two sons from Savio's home, spending the next two days with them. Prosecutors believe that he entered her home again early on February 29 and killed Savio.
At the time of her death, which authorities initially treated as an accident, a court was mulling how the couple's marital assets would be divided, and Savio was set to receive part of Peterson's pension and other support.
The defense contends Savio fell accidentally, hit her head, and drowned.
In Session's Michael Christian contributed to this report.