SYCAMORE, Ill. (AP) — A northern Illinois judge has denied a man’s request to withdraw his guilty plea in the 2010 death of a Northern Illinois University student.

The (DeKalb) Daily-Chronicle reports that the ruling means 41-year-old William Curl will continue to serve his 37-year prison sentence for the murder of 18-year-old freshman Antinette Keller. Curl had asked a judge to throw out his guilty plea and order a trial.

Judge Robbin Stuckert wrote that Curl’s petition didn’t establish that his constitutional rights were denied. Curl argued he wasn’t “right in the head” when he talked to police after his arrest.

Curl filed a petition in 2015 asking for post-conviction relief. In May he was granted a hearing that was held last month.

Keller, of Plainfield, was last seen Oct. 14, 2010. Her burned remains were later found at a park.