Jurors in Ottumwa said Tuesday they could not come to a unanimous decision on Robert "Gene" Pilcher's guilt, the Ottumwa Post reported. It was their third full day of deliberations.
Judge Richard Meadows read them instructions they heard before they began deliberations on how to discuss the case and the importance of a unanimous decision.
Deliberations were to resume Wednesday morning.
The victim, Mary Jayne Jones, 17, of Ottumwa was found in a farmhouse near Blakesburg, while the owner was on vacation in 1974, according to the website Iowa Cold Cases. Jones had come to Iowa from North Carolina to visit her sister and decided to remain.
Pilcher, 67, of Des Moines had been questioned by police years earlier. But he was not charged with killing Jones until 2012, although he has a history of arrests and convictions for other crimes.
Investigators said Pilcher was linked to the crime by technology not available in 1974. In 2011, the state Department of Criminal Investigation examined evidence from the killing for DNA evidence and say they got a match to Pilcher.
Judith Cabanillas, one of Jones' two sisters, told Iowa Cold Cases in a 2012 email after Pilcher's arrest that her family was "in shock."
"Our family has waited 38 years for this man to be arrested," she said.
In her email, Cabanillas praised Iowa investigators for preserving the evidence, remaining dedicated to solving it and keeping the family informed as years and decades passed.