FILE - In this 1973 photo provided by Judith Cabanillas is her sister, Mary Jayne Jones, a year before the 17-year-old girl was found dead in an Iowa farmhouse. A judge declared a mistrial Friday, Jan. 30, 2014 after jurors couldn’t reach a verdict in the case against Robert "Gene" Pilcher who was charged with first-degree murder in the April 9, 1974 slaying of 17-year-old Jones. (AP Photo/Courtesy Judith Cabanillas, File)

OTTUMWA, Iowa - After 40 years of seeking justice, the family of a 17-year-old girl beaten and shot to death at an Iowa farmhouse in 1974 will have to wait a little longer.

A judge declared a mistrial Thursday in the case of Robert "Gene" Pilcher, who was charged with first-degree murder in the death of Mary Jayne Jones. Jurors said they could not agree on whether Pilcher was guilty after a week of deliberations.

The outcome of the trial disappointed Jones' relatives, who had travelled from across the U.S. to attend the trial at the Wapello County Courthouse in Ottumwa. In a statement Thursday afternoon, they said they remained convinced that Pilcher was guilty of a "brutal and senseless murder" despite the jury's split, and called on prosecutors to continue pursuing the case.

"Obviously we wish that in this trial there would have been some justice for my sister, Jayne, and a guilty verdict, but I do not think that any of us will give up on seeing justice in this matter," Jones' sister, Judith Cabanillas, wrote in an email to The Associated Press.

After granting the mistrial, Judge Richard Meadows said Pilcher would face a second trial on March 25. Prosecutors indicated that they would retry Pilcher, who is back in the county jail.

Jones grew up in North Carolina and moved to Ottumwa in 1973 to live with a sister. Remembered as a free spirit, Jones stayed longer than she anticipated, got a job as a waitress at a popular drive-in restaurant and started dating.

Investigators say she was last seen at a downtown Ottumwa bank on April 9, 1974. Hours later, her naked, bruised and bloody body was discovered on a bed in a farmhouse down a gravel road about seven miles away. Investigators say she was beaten with a shotgun found broken in the home, possibly sexually assaulted and then shot at close range with a rifle — once in the heart, once in the head.

Pilcher, then a 27-year-old who worked as an exterminator and was involved in the Jaycees, became a prime suspect right away. The house was owned by his cousin, who was out of town at the time.

Four days before Jones died, a barmaid said that Pilcher had lured her to the same bedroom where Jones was found, handcuffed her and forced her to perform oral sex. Pilcher was charged with sodomy and perjury in that case, but investigators could not find evidence to link him — or anyone else — to Jones' death and the case went cold.

A cold case unit started by the Iowa Division of Criminal Investigation re-examined evidence in 2010 using tools that were not available in 1974.

Forensic testing linked Pilcher's DNA — by then in a database of known felons — to three semen stains left on the blanket where Jones' body was found. Pilcher was arrested in November 2012.

Prosecutors suggested the crime was sexually motivated, saying that Pilcher was attracted to Jones and had asked her out when he went to the drive-in. They noted similarities between the attack on the barmaid and the death of Jones.

But Pilcher's lawyers argued that the DNA evidence didn't prove that he killed Jones, noting that it could have been left there during the sexual encounter with the barmaid. Even the prosecution conceded two of the stains likely were from that.

The defence also argued that prosecutors failed to identify another source of male semen on the blanket, did not offer any witnesses putting Pilcher and Jones together outside of the restaurant and did not prove that he had handled the weapon used to kill her.

And they said Jones had a solid alibi. Witnesses saw him at different places around Ottumwa, including a Jaycees office he directed.

News from © The Associated Press, 2014