The victim's family is angry about the deal.
Relatives of victim Antinette Keller were not present in court, a show of protest according to a family spokesperson. But prosecutors say the plea deal guarantees significant prison time for the victim's killer.
Friends of the victim's family left the court in tears as 36-year-old William Curl flashed a peace sign as he was driven back to jail.
During the hearing, as Curl stood before a judge, his sister from the back of the courtroom yelled, "Don't take it, Billy! They're railroading you," referring to the plea deal.
"I think that was an unfortunate reaction by his sister," said DeKalb County public defender Tom McCulloch. "Expected, it's natural, but unfortunate."
The deal comes two and a half years after the charred remains of 18-year-old Antinette Keller of Plainfield were found in a DeKalb Park.
Prosecutors say curl was known to frequent that park gave conflicting statements to police and fled the state before his arrest.
Still, prosecutors called the case "challenging,"
"It would have involved a trial without occurrence witnesses, a murder weapon, a time of death, a cause of death, limited forensic evidence, and no confession to the crime of murder," said Richard Schmack, DeKalb County States Attorney.
Under the plea agreement, Curl must serve all 37 years of his sentence.
But the plea is a so-called "Alford plea," which essentially means he doesn't have to admit guilt, something the State's Attorney said he agreed to in exchange for a longer sentence.
Wednesday, Curl's attorney said his client maintains his innocence.
"He has a story about that and about how he was concerned that the cops would railroad him," McCulloch said.
Wednesday, former DeKalb State's Attorney Clay Campbell, who worked on the case for two years before losing last fall's election, called the 37 year sentence "outrageous."
"I think it diminishes human life, and it dishonors the memory of the victim," Campbell said.
Curl will be 71 years old when his sentence is complete. Exactly where he will serve his time has not yet been announced.
Prosecutors say it's one of the longest terms ever secured in the county by plea deal, but it is not enough for the family.