The couple, who said they have known Peterson for about 16 years, said they became suspicious after Stacy disappeared last October and agreed to help state police with the investigation.
Wawczak and Stark say Peterson mocked the police investigating the death of his third wife, Kathleen Savio, whose death was originally ruled an accidental drowning.
According to Stark, Peterson said, 'She was in a dry bathtub,' and that he called police 'a bunch of idiots.'
After Stacy disappeared, Savio's body was exhumed and her death was reclassified as a homicide. Wawczak says Peterson commented, "I should have had that (expletive) cremated. It would have cost me less and I wouldn't be going through this trouble."
Peterson is disputing the couple's comments.
"They stormed off mad one day when I wouldn't lend them money," Peterson told the Sun-Times. "They wanted some big money from me."
On Wednesday morning, Drew Peterson spoke to reporters through his front door. He deferred questions to his attorney, Joel Brodsky.
"He is adamant he never said such comments, never will appear on court, never said it even off tape," said Brodsky.
Brodsky says the couple went to the Sun-Times with their story because they're about to lose their home and they want money.
"They see other people making money off the story with the National Enquirer or a book or some things like that. They thought this sensational story might be a way for them to make some money and get out of their financial problems," said Brodsky.
Wawczak and Stark told the newspaper, "Peterson said he wasn't worried about them finding Stacy's remains down the road because he figured by that time, he would have been tried and acquitted."
"Before Stacy's remains are found? I just think it's weird because he said she ran off with another man, and, you know, obviously we know she didn't, but that was his line in the beginning," said Stacy's sister Cassandra Cles.
Cales and family spokesperson Pam Bosco say they are grateful that Wawczak and Stark came forward to help police.
"People are actually starting to come forward. They see the real Drew," Cales said.
"They have to respect themselves for putting themselves in that situation. If you want to do it, you're going to do it, regardless of the risks. We're talking about two wonderful women, mothers, who are no longer with us. That is the right thing to do," Bosco said.
And the family Savio is grateful as well.
"A lot of the stuff that I read, I found disgusting. But I really wasn't surprised by it, knowing Drew," said Savio's niece, Melissa Doman.
Paula Stark smoked a cigarette on the steps of a relative's Bolingbrook home Wednesday night, declining comment.
"They're not lying. I'm proud of what they did and I back them 100 percent," said niece Terry Stoll. "There's no financial motivation."
Attempts to reach the informant couple were unsuccessful Wednesday morning. But one neighbor, who says she's known Wawczak and Stark for many years, says the couple has no reason to lie.
"I don't think they're lying, period. I think what they did was really good. Someone needed to step in and do something. I'm glad it was them," said Linda Miller, friend of Stark and Wawczak.
Wawczak said he had no reservations about turning informant for the police, but his wife was afraid.
"I talked her into it," he said.
Wawczak said his own father was slain during a holdup of his gas station in 1975. The killer was found thanks to a woman who reported the license number of the getaway car. He said that's partly why he agreed to help police investigating Peterson.
Peterson has denied any involvement in Savio's death and Stacy's disappearance. He has not been charged with any crime.
The Associated Press contributed to this report. All rights resevered.