The allegations were made at a hearing today where Peterson's lawyers were asking for a reduction in their client's $20 million bond, according to the report. A judge refused to reduce the bond.
Assistant District Attorney John Connelly said after the new allegations were bared, "I believe the likelihood of a conviction is strong."
Prosecutors gavea preview of their case today and said Savio's death was staged to make it look like an accident.
The state also claims Peterson tried to solicit a hit on Savio in 2003, but did not elaborate. Prosecutors indicated they have evidence that would be presented in court.
In addition, the state told the court that Peterson knew fact of the case that only the killer would know.
On Thursday, police realized that were facing major obstacles in identifying the body found along an Illinois river bank near Peterson's home since the corpse is missing its head, arms and skin.
The office of Will County Coroner Patrick K. O'Neil said the body -- which many believe could be that of either Peterson's missing fourth wife Stacy -- was clad in only women's underwear and shreds of blue jeans that held a small amount of money.
Since the corpse lacks a head, hands or feet, it has complicated identifying the body through dental records or prints.
"The partial skeletal remains consisted of a rib cage, spinal column and partial left and right femur bones," the coroner's office said.
The lack of skin has made it more difficult to obtain DNA. A coroner and a forensic anthropologist are working together to confirm the gender of the corpse and are expected to test the bone marrow to try and identify the remains, sources told ABC News affiliate WLS's Amy Jacobson.
The coroner's office said it will take at least two weeks to obtain the DNA and determine its match.
They are also trying to determine whether the head was severed before or after death, O'Neil said. Police are also searching for the body's head and other body parts.
Though officials acknowledge the body could be someone else's the similarities between Stacy Peterson and another missing woman, Lisa Stebic, are numerous. Both are of similar height and weight and both have had Cesearan sections after giving birth. They also disappeared within months of each other.
The discovery Wednesday of the decomposing body near Peterson's Illinois home has the potential to blow huge holes in his claim that his fourth wife simply ran off with another man.
But Stacy Peterson wasn't the only local woman who disappeared in 2007. Lisa Stebic, a mother from nearby Plainfield, Ill., disappeared in April 2007.
"My honest feeling is hope the body is ID'd if it was Lisa or Stacy," Stebic's cousin Melanie Greenburg said. "I hope one of our families gets closure from this."
But the fact that the decomposing body was found less than a mile from a blue barrel could be significant, as Peterson's stepbrother told "Good Morning America" in March that he helped Peterson move a heavy blue barrel from the Petersons' home into their SUV shortly after Stacy Peterson disappeared.
"I know he killed Stacy," said Peterson's stepbrother Thomas Morphey.
Area resident Michelle Williams spotted the blue barrel in the river earlier this week and notified police.
"A blue barrel in the river is something people would want to know about, especially police," Williams said. "When we first saw the blue barrel we first thought of Stacy Peterson."
Drew Peterson has denied any involvement in Savio's death and Stacy Peterson's disappearance, even as the majority of public opinion remains suspicious. Peterson has pleaded not guilty to first-degree murder charges in the death of Savio, whose body was found in her empty bathtub with a gash in the back of her head. He remains jailed on $20 million bond.
Investigators say the partial remains of a small woman clad only in underwear were found by a barge clean-up crew on the bank of the Des Plaines River near rural Channahon, Ill.
The Will County coroner's office said it will conduct an autopsy today and investigators say DNA will be crucial in identifying the body.
"If it isn't Stacy today," Peterson neighbor Sharon Bychowski said," we'll keep looking for her."
Twists in Peterson Case Just Keep Coming
Peterson's Monday arraignment in the Savio case was cut short when prosecutors made a surprise request for a new judge to oversee the case.
His attorneys have vowed to get the $20 million bond reduced but must wait in the wake of the prosecution's request that Judge Richard Schoenstedt be removed from the case, citing suspected bias against the state.
A spokesman for the Will County State's Attorney's Office declined to elaborate on the request.
In November, Schoenstedt dismissed felony gun charges against Peterson after prosecutors refused to give defense attorneys internal documents that described communication between the Illinois State Police and prosecutors. Those documents reportedly led to the decision to arrest Peterson on the gun charges.
After Monday's hearing, Peterson's attorney, Joel Brodsky, criticized prosecutors.
"A motion by the state for a substitution of judges is almost unheard of, extremely rare. And I just think it indicates to us the weakness of the state's factual position," he said. "It shows that they don't want to deal with this case on the facts but want to try to get this case to a place where they're more comfortable, as opposed to having a judge ... who's gonna listen to both sides."
Savio's death was initially ruled a drowning accident but a second autopsy, conducted in 2007 after the disappearance of Peterson's fourth wife, ruled it a homicide. Peterson is also a suspect in the disappearance of his fourth wife, Stacy Peterson.
Peterson has made headlines not only for his legal troubles but for his jokes about it.
"Drew's personality is, I'll say ... unique," Brodsky said earlier today on "Good Morning America." "But he's honest."
If Peterson does take the stand in his defense, Brodsky said he thinks that honesty would only help him. But finding an impartial jury, he said, could be difficult.
Peterson has said he expects to be found innocent of Savio's murder and has maintained a seemingly cavalier attitude toward his May 7 arrest.
As he was being led into court, Peterson, handcuffed and wearing a red jumpsuit, joked with reporters, saying, "What about this bling? Look at this bling. Three squares a day in this spiffy outfit. How can you beat that? Look at this bling. My God."
Even when he was first arrested, he joked, "I guess I should have returned those library books."
Last week, Peterson, who is being held at the Will County jail, defended his behavior.
"Well, there is no book written on how I'm supposed to act," Peterson told NBC's "Today" show. "Would it be better if I hid my head down and tried to hide my face and hunched over and tears in my eyes? I mean, no, that's just not me."
Drew Peterson Also Suspected in Disappearance of Stacy Peterson
Peterson is also considered a suspect in the disappearance of his fourth wife, Stacy. A law enforcement source said the special grand jury that indicted Peterson for Savio's death is continuing to hear evidence in the Stacy Peterson case.
If a murder indictment is handed down for the Stacy Peterson case, experts said it could vastly change the case against Drew Peterson.
"Then I think the prosecution will combine both cases, and each case will sort of feed off the other and will present a powerful picture to both a trial judge and a jury that this guy is a serial murderer," legal analyst Dana Cole told ABC's "Good Morning America" last week.
Peterson told "Today" that he will "probably be found innocent" of Savio's murder.
Brodsky has aid he expects to challenge a new Illinois state law that could prove vital to the prosecution's case.
Prosecutors are hoping they can enter into evidence writings from Savio when she was in the midst of her divorce from Peterson, that she feared her husband's "next step is to take my children away or kill me."
A new Illinois state law allows such statements only if the witness was killed to prevent him or her from testifying.
The Associated Press contributed to this report.