Now a 62-year-old inmate at the Iowa State Penitentiary, Beeman has claimed since 1980 that his confession was false and that he signed it only to end an unrecorded interrogation that left him scared and confused. But courts have upheld the confession.

His lawyers filed a motion last month seeking DNA testing on a sexual assault kit that included sperm and blood recovered from Winkel and several items of her clothing found at the scene.

But officials with the Division of Criminal Investigation and Muscatine County Sheriff’s Office said in court filings last week that they have searched and cannot find the evidence. They say retired investigators who worked the case also have no idea of its whereabouts. Muscatine County Attorney Alan Ostergren has asked a judge to deny the request for DNA testing.

“There is nothing that can be done about the inability of the agencies to locate the evidence,” he wrote, noting that police weren’t required to keep evidence that could be tested for DNA until Iowa law changed in 2005.

A judge has scheduled a hearing next week on the matter.