His fourth wife, Stacy Peterson, is missing, and police say they consider him a suspect in the disappearance, which they've dubbed a possible homicide. But he hasn't been charged and has repeatedly said he thinks Stacy Peterson ran off with another man.
Savio, 40, was found dead in a dry bathtub in her home in February 2004, her hair soaked in blood from a head wound, just before the couple's divorce settlement was finalized. At first, her death was ruled an accidental drowning.
But when Stacy Peterson, who was 23 at the time, vanished in October 2007, Savio's family became suspicious and had Savio's body exhumed. Authorities later declared her death a homicide made to look like a drowning.
Peterson's arrest comes as welcome news for Savio's family.
Her nephew, Charlie Doman told CBS News, "Finally, we're being heard, and the investigation is moving forward now."
On The Early Show Friday, he said Peterson hasn't shown any remorse or sorrow over Savio, noting, "The day we buried her, he went over to the house with a big truck and pulled everything out of the house. So I don't think he had any remorse at all."
Prosecutors say they'll test a new Illinois hearsay law in the case, reports CBS News correspondent Cynthia Bowers. It allows murder victims' words to be used against their accused killers. Bowers says prosecutors plan to cite Savio's predictions to relatives that Peterson would to kill her.
"This is very important," CBS News legal analyst Lisa Bloom said on The Early Show Friday. "And the state attorney mentioned it (Thursday) in his press conference. Illinois changed its law last year to allow in(to evidence) statements from murder victims, exactly as happened here. Kathleen Savio told her sister, 'If anything happens to me, Drew Peterson killed me.' Stacy Peterson, by the way, told her sister the identical thing. Kathleen Savio also wrote a letter to a prosecutor (saying), 'He would do anything to get custody of our kids,' - remember, they were in a bitter divorce - 'including kill me.' Under the new law, those statements may come in(to evidence). There has to be a hearing. I'm sure it will be hard-fought. But if prosecutors can get that in, that would be very helpful to them."
One of Peterson's attorneys, Andrew Abood, says the indictment that preceded Peterson's arrest wasn't a complete surprise.
"There was tremendous pressure for the government to do something in this case," Abood says. But he added that one of the sons Peterson had with Savio has "provided a lock-tight alibi" for his father, who faces up to 60 years in prison if convicted.
In an appearance on The Early Show last month, 16-year-old Thomas Peterson appeared alongside Drew and , saying, "I highly do not believe that my dad had murdered my mom. Because, first off, he wasn't there, he was with us during that period of time."
Bloom said Thomas Peterson "certainly can be called to testify. He would have been 10 years old at the time, and I'm sure he'll be questioned as to how accurate his memory is, as to specific times. Drew Peterson and Kathleen Savio lived near each other. It would not have taken long for him to drive over there, commit this homicide and drive back."
On The Early Show on Friday, another Peterson lawyer, Joel Brodsky, said forensic evidence his side will introduce will show that Savio's death was indeed an accident.
Peterson, 55, was scheduled to be arraigned Friday on charges of first-degree murder.
Brodsky also told co-anchor Maggie Rodriguez Peterson would plead "not guilty to all charges, obviously."
"I think," he continued, "the main point in this case is going to be forensic. We still believe that never has been, a homicide, that kathy's death was accidental, and we believe that when we get our pathologist in and have him review everything, that ... that will be upheld, that, beyond a reasonable doubt, it was an accident. ... This is at best a weak circumstantial case."
Bloom predicts an indictment of Peterson in the Stacy Peterson case. "The grand jury is still convened," she pointed out. "The state attorney said (Thursday) they will still meet every Thursday, as they have for the last year, continue to investigate the disappearance of Stacy Peterson. You do not need a body in Illinois to get a murder conviction. It certainly helps, but it's not legally required. I expect them to come back with charges as to Stacy Peterson, as well."
Peterson has seemed to relish the spotlight since Stacy Peterson's disappearance, appearing in a People magazine cover story and on multiple national talk shows.
His arrest, Bowers points out, came just a day after he announced that he was moving to Las Vegas to participate in a reality show set, in all places, at a brothel. He was to play a security guard.