Peterson, 58, is charged with the first-degree murder of his third-wife, Kathleen Savio. He pleaded not guilty to the charge.
Mary Pontarelli lived next door to Savio in 2004 and found her body inside a bathtub. Prosecutors believe Peterson staged the scene to make it look like an accident. The defense is trying to cast doubts on the state's theory.
Pontarelli testified that on that day Peterson was "worried" and "upset." When asked about Savio, she said, "She's tough. She wouldn't let someone hit her, without hitting back."
Pontarelli was called to the stand after Judge Edward Burmila denied the defense's motion for a directed verdict Monday morning, saying "a finder of facts could return a guilty verdict."
A directed verdict would have given Judge Burmila the opportunity to render a not guilty verdict before the jurors deliberate or the defense presented a case. Directed verdicts are rare, and indicate that the prosecution failed to prove its case.
"It's very rare to get a directed verdict when you have a sitting jury, especially in a murder trial" Joe Lopez, defense attorney, said.
The prosecution had rested earlier on Monday after reading a letter written by Savio in which she states she feared Peterson would kill her. The prosecution presented a case full of hearsay evidence with no physical evidence linking Peterson to the Savio murder.
"They haven't done anything that placed Drew Peterson at the scene of her death. They haven't put him in the house or the bathroom, they haven't shown how it was gone as opposed to say gee whiz she drowned and he did it," defense attorney Joel Brodsky said.
"It's very strong circumstantial case," court observer and attorney Kathleen Zeller said.
The defense is expected to call around a dozen witnesses over the next two or three days. One of them will be Peterson's son, and the other could be the defendant, himself, although his attorneys have advised him not to testify.
"I don't think Drew is afraid of testifying. I think he would like to if it's the right thing to do. But once again that's a decision that hasn't been made yet," Brodsky said.
Throughout the last week of trial, jurors have showed solidarity by wearing the same colors. On Monday, they wore sports jerseys, which led the judge to joke with them. Judge Burmila, a White Sox fan, called them "intelligent" since no one wore a Cubs jersey.
"Maybe they ran out of clothes and wanted him to wear something different," Lopez said.
"If the families are not offended by it, I think it is fine," Zellner said.
Peterson, 58, is charged with first-degree murder in the 2004 death of Savio, whose body was found in a bathtub. Originally declared an accident, the case was reopened after Peterson's fourth wife, Stacy Peterson, disappeared in 2007.
Peterson is a suspect in Stacy's disappearance, but no charges have been filed. He maintains his innocence in both cases.