"When your child dies, a piece of you ceases to exist," read a portion of a statement from the girl's mother that was read by a state's attorney official.
There was no apology or any statement from Curl, McCulloch said. Even though he entered a plea in return for the 37-year sentence, Curl has never admitted to killing the teenager.
"He maintains his innocence," said McCulloch, explaining that Curl entered what is called an Alford plea, which acknowledges that prosecutors could likely prove the charge filed against him.
Curl's sister, Moira Curl, loudly voiced her displeasure during Wednesday's proceeding, urging her brother not to accept the plea deal: "Billy, don't take it. They're railroading you," she yelled before being removed from the courtroom by deputies.
Keller, an art student from Plainfield, was last seen before she headed to a park and nature preserve near the university. Burned remains were found in the park two days later, and forensic experts later confirmed the remains were human. Police found Keller's burned clothing and her cellphone near the remains, prosecutors said.
Police said Curl was a person of interest because he was known to frequent the park. They said he became a suspect after he failed to show up for further questioning and fled to Mexico in a stolen SUV. Investigators said Keller's death was a crime of opportunity and Curl did not know her.