By Adam Kirby

JOLIET, Illinois (Reuters) - Prosecutors on Tuesday asked the jury in the Drew Peterson trial to give weight to witnesses who said the former suburban Chicago police officer threatened his third wife and was capable of murder, while defense lawyers stressed the lack of physical evidence that he killed her.

During closing arguments in the trial of Peterson, accused of killing his third wife Kathleen Savio, Assistant State's Attorney Chris Koch conceded that the evidence against Peterson was largely circumstantial. But Koch said that witness testimony proved beyond a reasonable doubt that Peterson had a motive, intent and ability to murder Savio.

"Keep in mind common sense," Koch said. "When you use your common sense, it is obvious this man killed Kathleen Savio."

Koch said the combined weight of the evidence from witnesses should be enough to find Peterson guilty beyond reasonable doubt.

Peterson is accused of killing Savio in 2004 during a contentious divorce and then staging her death to look like an accidental drowning. Savio was found dead in a bathtub and investigators initially ruled it accidental. Suspicions were raised when Peterson's fourth wife, Stacy Peterson, disappeared in 2007. Savio's body was exhumed and reexamined, and Peterson was charged with murder.

Little physical evidence links Peterson to Savio's death, and the prosecution's case has relied largely on testimony from several people who said Peterson threatened Savio, tried to hire a hit man and said he could make her death look like an accident.

Defense attorney Joe Lopez said the jury should find Peterson not guilty because of the lack of physical evidence. Lopez referred to testimony that Peterson made threats as "rumor and innuendo.

"Is that what it's come to, that we can convict somebody on speculation?" Lopez said.

The Peterson case has received national attention in part because of a popular Lifetime television network movie, "Untouchable," starring Rob Lowe.

Peterson is the sole suspect in the disappearance of his fourth wife, Stacy Peterson, who has never been found. His first and second wives have remarried.

The Will County jury of seven men and five women are expected to begin deliberations on Wednesday.

(Editing by Greg McCune and Cynthia Osterman)