A man who spent nearly 30 years in prison for the 1984 sexual assault and murder of a 15-year-old suburban Chicago girl left prison a free man on Wednesday, after a judge threw out charges against him.

Christopher Abernathy, 48, was released after a judge agreed to a prosecutor’s request to vacate his life sentence, Illinois corrections department spokesman Tom Shaer said. Abernathy was sentenced to life in 1987, but DNA testing last August excluded him from the case.

“He is elated and just so happy that he’s able to go home, that he’s free and gets to be with his family,” said Abernathy’s attorney, Lauren Kaeseberg. She said Abernathy did not make a statement as he left the Stateville Correctional Center near Joliet.

Abernathy was represented by the Illinois Innocence Project based at the University of Illinois-Springfield. His attorneys said the person who accused him has recanted the testimony.

Cook County state’s attorney Anita Alvarez said a reinvestigation of the case turned up “several troubling aspects … including the fact that Abernathy may have suffered from a diminished mental capacity and that he wrote and signed a confession that was void of any significant details of the crime.”

Abernathy was convicted in the 3 October 1984 sexual assault and murder of Kristina Hickey, a 15-year-old high school student who went missing after a choir concert at Rich East High School in Park Forest, according to the Illinois Innocence Project. Her body was found two days later under bushes near a shopping centre.

Attorneys for Abernathy said he was arrested more than a year later and signed a statement implicating himself after more than 40 hours of interrogation. Abernathy later said he was coerced into signing the document.

Abernathy had documented learning disabilities and left school at age 15, his attorneys said.

“He was able to be coerced into signing a confession after being told that was the only way he could go home and see his mother,” Kaeseberg said.

The case is part of the prosecutor’s Conviction Integrity Unit that was created in 2012 to reinvestigate wrongful or questionable convictions.

Kaeseberg said Abernathy had no concrete plans for now. He must get acclimated to life outside prison, she said, adding that the days and weeks that follow his release will be critical to his success.

“We know the road ahead will be difficult for him after spending his entire adult life imprisoned for a crime he did not commit,” Illinois Innocence Project founding director Larry Golden said.