If released, Lay faces lifetime parole, court documents show. He has been credited for 168 days already served.
Court records filed in Butler County Area II court said Lay confessed to killing Risner, a mother of three sons.
Police were called shortly before 4 p.m. Feb. 4 on a report of an unresponsive person. Risner was pronounced dead at the scene, and her death was ruled a homicide by the Butler County Coroner’s Office.
In an application for a warrant to search the house, police said Risner suffered a gunshot wound to the head.
The house and Risner had been the subjects of a drug investigation by the Warren County Drug Task Force for months before the homicide, according to court documents.
Mattox, who faces two charges of tampering with evidence, is scheduled to be back in court Aug. 5 for a pre-trial hearing.