Prosecutors and defense attorneys were expected to sit down with a judge Wednesday and say they had reached a deal.
Relatives of victim Antinette Keller said they were devastated by that news as they left the DeKalb County court house Tuesday without comment.
But Keller's mother, Diane, expressed frustration with the plea deal for 36-year-old William Curl in a Facebook post:
"They knew he was guilty and the evidence showed a strong case. Instead, a criminal gets the option of a lighter sentence for a guilty plea. Meanwhile, Roger and I, and all of the Keller family get a life sentence. Thanks for nothing," she wrote.
"We were anticipating trial... I live here. There are a lot of questions unanswered ... And have been unanswered since Toni's murder. This plea bargain is not going to answer that," said family friend Thelma Holderness.
Before she went missing in October 2010, the 18-year-old NIU freshman told friends she was going for a walk in a nearby park. Antinette's charred remains were found days later. Police say she'd been beaten and raped prior to her death.
Investigators say Curl frequented the park and called police to report the fire.
As for his alleged motive, investigators say it was a crime of opportunity.
Federal marshals arrested Curl in Louisiana after several days on the run.
"The decision finally is his. The decision is usually based on having some control on the outcome. One thing for certain at trial, you don't control the outcome. The judge has some control of the outcome, and the jury has the ultimate control," public defender Bill McCulloch said.
The plea deal calls for Curl to serve 37 years in prison, requiring that he serve 100 percent of that sentence. There would be no chance to get out for good behavior.