JOLIET, Ill. (AP) -- Just two days after his third wife's body was found in a bathtub, Drew Peterson sat on a card-table chair next to his tearful fourth wife and corrected at least one of her answers as state police interviewed her about the death, the lead investigator at the time told jurors on Wednesday.

The testimony came on a drama-filled day as prosecutors in Peterson's murder trial won an important legal victory over normally barred hearsay evidence at the core of this unique case. Prosecutors also continued to try and show that the investigation into the 2004 drowning of 40-year-old Kathleen Savio was badly botched.

Retired Illinois State Police sergeant Patrick Collins testified that Peterson -- charged in Savio's death only after his fourth wife, 23-year-old Stacy Peterson, went missing in 2007 -- had his hand on Stacy's knee and his arm around her shoulder during the interview in the basement of the couple's home.

"He sat very close to Stacy as we proceeded to ask questions," Collins recalled. "She was very distraught."

Also Wednesday, a key prosecution witness began sobbing and left the courtroom to regain her composure after she started to talk about how Savio once said Drew Peterson had bragged, "'I could kill you and make it look like an accident.'"

When Savio's friend returned minutes later, she told jurors that Savio had described how Peterson broke into her house and made the threat at knife point. Anderson, who lived at Savio's house temporarily, said Savio was so afraid, she kept a knife under her mattress.

During cross-examination, defense attorney Joe Lopez raised his voice, pressing Anderson repeatedly about why -- if the threat was so unsettling -- she didn't move out of Savio's house.

"You didn't move out, did you? ... You did nothing ... because you didn't believe her, that's why," Lopez shouted over the objection of prosecutors.

"Sir, no one listened to Kathy," Anderson added later.

Judge Edward Burmila handed prosecutors the legal victory by allowing Anderson's hearsay testimony. At first, the judge seemed to signal he would bar it, prompting an angry James Glasgow, the Will County state's attorney, to raise his voice.

"This evidence should have life!" the normally monotone chief prosecutor shouted. The jury was not in the room.

With no physical evidence at their disposal, hearsay statements like Anderson's are at the heart of the prosecution's presentation to jurors. Without them, most legal experts say the state stands virtually no chance of a conviction.

Burmila, who once lost a political race to Glasgow, criticized the prosecution for poorly addressing the complex legalities surrounding hearsay, but surprised many -- even eliciting gasps -- by allowing then testimony.

Addressing reporters at the end of the day, Glasgow was clearly thrilled the ruling had gone his way.

"Judge Burmila made an historical ruling today," he said.

Lopez said his client was disappointed in the ruling.

"He's upset," Lopez said. "But you have to deal with the cards they give you."

Earlier in the day, the 58-year-old Peterson sat forward attentively while Collins was on the stand, once standing and appearing to suggest a question to his attorney.

According to Collins, Peterson asked if he could sit in on the 2004 interview as a "professional courtesy," and the 26-year state police veteran agreed. Collins conceded it was unusual to let one potential witness sit in on the interview of another, saying he had never done it before and never did it again.

Outside observers may be inclined to link Savio's death to Stacy Peterson's disappearance, but jurors aren't supposed to make any such links. Burmila has prohibited prosecutors from telling jurors Stacy Peterson is presumed dead or that Drew Peterson is a suspect -- though isn't charged -- in her disappearance.

Collins testified that during the interview at the Petersons' home, located just blocks from Savio's, Stacy Peterson became increasingly emotional.

"She became shaken and started to cry," Collins said. "And (so) we shut the interview down." He said he did not interview her again.

During cross-examination, defense attorney Joel Brodsky suggested that she was upset because Savio's death meant she would now have to take on the extra burden of caring for Savio's two children.


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