Joliet, Illinois (CNN) -- Attorneys for Drew Peterson, a former Chicago-area police officer accused of murdering his third wife, argued during opening statements Tuesday that their client spent his career protecting the public and that murder accusations are groundless. 

"Kathy slipped, fell, hit her head in a household accident, and drowned. Case closed," said attorney Joel Brodsky. 

Kathleen Savio was found dead in a bathtub in 2004. Peterson also remains under investigation in the October 2007 disappearance of his fourth wife, Stacy Peterson. 

Prosecutors, meanwhile, argued that Peterson was motivated to kill, at least in part, by his desire to avoid settlement payments to his ex-wife. 

"This (is) not a case where you'll have DNA, fingerprints, or a videotaped confession . . . (But) when you've heard all the evidence, you'll be able to determine that Drew Peterson killed Kathleen Savio beyond a reasonable doubt," said Will Country State's Attorney James Glasgow during his opening statement. 

Prosecutors called Mary Pontarelli, a neighbor, as their first witness. Her voice cracked on a couple of occasions as she described finding the body of Savio, her friend. 

Court is scheduled to resume Wednesday morning. 

A jury of seven men and five women, chosen over two days last week, will decide Drew Peterson's fate during the trial in Joliet, Illinois, which is expected to last about a month, according to his lawyer. 

Peterson, 58, was married to Savio in 2001 when he had an affair with then-17-year-old Stacy Kales, who later became Stacy Peterson. 

Savio and Peterson filed for divorce that October, and their relationship remained contentious for the next several years. 
Why not?
Savio and Peterson filed for divorce