The heart of the state's case is testimony from friends, relatives and acquaintances of the two women about things they allegedly told them about Drew Peterson. Such testimony, called hearsay, isn't usually allowed in court, but Illinois passed a law in 2008, dubbed "Drew's Law," that allowed it to be introduced at trials under rare circumstances.
In his more than hourlong closing, prosecutor Chris Koch went through more than half a dozen hearsay statements, including witnesses who testified Savio told them her husband repeatedly warned her he could kill her and make her death look accidental.
As he began his remarks Koch walked up to the defense table, pointed his finger at Peterson and boomed, "It is clear this man killed Kathleen Savio."
Punching his fist into his palm for emphasis, Koch said Peterson slipped into his estranged wife's suburban Chicago home just a few blocks from his new house in the early morning hours before March 1, 2004.
"He went into that house, pushed her down, held her down until she inhaled fluid and drowned," said Koch.
In the recurring mantra of his closing, Koch told jurors to use common sense in assessing Peterson's alleged threats and suspicious behavior in the days after Savio's death. Peterson, he said, went to Savio's house the day after her body was found there to wash blood from the tub.
"Are you kidding me?!" balked Koch. "What in the world is he doing there? Murders sometimes go back to the crime scene."
Defense attorney Joel Lopez countered that the state had presented "garbage evidence" during its five-week presentation of more than 30 witnesses.
Lopez told jurors that when they deliberate, they are required to hear a voice whispering to each of them that Peterson is innocent. He said they can't conclude Peterson is guilty unless the evidence is overwhelming and compelling.
"You have to find he is guilty beyond a reasonable doubt not maybe, not probably (he did it)," he said. "Are we going to convict someone on speculation? ... This is America!"
Lopez constantly doubled back to his central argument: The state hadn't even proved Savio's death was a murder.
"The framers of the Constitution would barf on this evidence," said Lopez.
But Koch told jurors it would be impossible for Savio to have received the gash on the back of her head and 14 bruises on the front of her body unless someone had attacked her.
"How can you get (all those wounds) in one fall?" he asked. "You can't."
Peterson, 58, has pleaded not guilty to first-degree murder. If convicted, he faces a maximum 60-year prison sentence.
Judge Edward Burmila decided to send jurors home for the night after closing arguments ran longer than expected. Burmila said he would read instructions to the jury first thing Wednesday morning. The seven men and five women will then withdraw to a jury room to begin their deliberations.
Peterson is suspected but hasn't been charged in Stacy Peterson's disappearance, and prosecutors were barred from mentioning or hinting that that she is presumed dead and that her husband is the lone suspect in her disappearance.