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. 
What is the man being accused of?
What is his name?
Who do they suspect he murdered?
What is her name?
Does he assume guilt?
Has he remarried?
What is the name of his fourth wife?
Does she support her husband?
Why not?
Where is Stacey?
What reason do they believe Peterson has for harming his wife?
Will he be having a trial?
How old is the accused Peterson?
Was Stacey an adult when they met?
How old was she?
What year did he wed Savio?
Who is the neighbor that is being called to testify?
How long did it take to choose the jury?
Are there an even number of men and women on the jury?
How many women are there?
murder
officer accused of murdering his third wife,
Drew Peterson
 for Drew Peterson, a former Chicago-area police officer accused 
his third wife
r accused of murdering his third wife,
Kathleen Savio
Kathleen Savio was found dead
no
client spent his career protecting the public and that murder accusations are groundless. 
yes
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. 
Stacy Peterson
Stacy Kales, who later became Stacy Peterson. 
no
 their relationship remained contentious for the next several years.
Savio and Peterson filed for divorce
Savio and Peterson filed for divorce
she disappeared
disappearance of his fourth wife, Stacy Peterson. 
to avoid settlement payments
by his desire to avoid settlement payments to his ex-wife.
yes
A jury of seven men and five women, chosen over two days last week
58
Peterson, 58
no
 he had an affair with then-17-year-old
17 years old
an affair with then-17-year-old Stacy Kales
2001
Peterson, 58, was married to Savio in 2001
Mary Pontarelli
Prosecutors called Mary Pontarelli, a neighbor
two days
A jury of seven men and five women, chosen over two days last week
no
A jury of seven men and five women, 
five women
A jury of seven men and five women