Jury selection begins Monday in the long-awaited trial of a Delphi, Indiana, man accused of killing two teenage girls as they hiked on a local trail in broad daylight in 2017.

The case drew national attention and remained a mystery for over five years until suspect Richard Allen was arrested in October 2022. He pleaded not guilty to murder.

Here's everything you need to know about the case.

The murders

On February 13, 2017, best friends Abby Williams, 13, and Libby German, 14, were enjoying a day off from school in their hometown of Delphi, a quiet small town of nearly 3,000 people in central Indiana.

They were on a trail, walking, talking and taking photos when they disappeared.

Their bodies were found the next day.

Abby, who was raised by her single mother, hoped for a career in forensic science.

Libby, a gifted athlete who was raised by her grandparents, wanted to work with the FBI and solve crimes.

Police have never revealed how the eighth-graders were killed.

According to a video recovered from one of the victim's phones, Abby or Libby mentioned “gun” when a man approached them, and an unspent .40 caliber cartridge was found less than 2 feet from one of the bodies, which followed a probable cause affidavit. But court documents also mention the involvement of a knife in the killings.

“Down the Hill”

After the shocking double murders, authorities released a clip of the suspect's voice – a recording of him saying “down the hill” – which was recovered from Libby's phone.

According to the affidavit, a man was seen and heard telling the girls, “Guys, down the hill,” and Abby and Libby then walked down the hill.

Authorities also released a grainy image of the suspect who they said was on the trail of the girls the day they disappeared. State police later distributed a short video clip recovered from Libby's phone that showed the suspect walking on the bridge near where the girls were last seen.

The arrest

The case remained unsolved for more than five years and preoccupied the residents of Delphi.

Police released various sketches of possible suspects, and authorities said that while investigating the case, they “discovered” a fake Snapchat and Instagram profile called “anthony_shots” in which the user used and tentatively used photos of a male model communicated with underage girls to meet them. The man believed to be behind the “anthony_shots” account was later identified and not linked to the murders of Abby and Libby.

Until Allen was arrested in October 2022, no suspect in the murders was named.

Community members were shocked to learn that the suspect was a 50-year-old husband, father and Delphi resident who worked at the local CVS.

“How can someone do this and then just go on living like nothing happened?” Libby's grandfather, Mike Patty, told ABC News hours after the arrest was announced.

Allen admitted to police that he was on the trail that day but denied any involvement in the murders, according to court documents.

Police analysis of Allen's gun revealed that the unspent cartridge, discovered just two feet from one of the victims, “had been passed through Richard M. Allen's Sig Sauer Model P226,” the probable cause affidavit said .

“When asked about the unspent bullet, (Allen) had no explanation as to why the bullet was found among the girls' bodies,” the probable cause affidavit states.

When Allen voluntarily spoke to police on Oct. 26, 2022, he said he had not allowed anyone to borrow that gun, which he said he had owned since 2001, the document continued.

Video from Libby's cell phone showed a man in a dark jacket and jeans on the trail. In an October 2022 interview, Allen told investigators that he wore jeans and a blue or black Carhartt jacket on the trail that day, and Allen's wife confirmed to police that he owned a blue Carhartt jacket, according to the affidavit.

Investigators believe Allen is the brash suspect seen on Libby's cell phone video. According to the affidavit, investigators also allege that he forced Abby and Libby down the hill to the spot where they were killed.

Investigators believe Allen was seen walking back to his car with “muddy and bloody clothing,” the probable cause affidavit said.

According to open court documents, Allen allegedly confessed to the murders several times in a prison phone call to his wife in April 2023.

“Shortly after” that call to his wife, Allen's attorneys filed an emergency motion saying his mental state had deteriorated and he should be transferred, saying Westville Correctional Facility was not suitable, the document said. He was evaluated by two psychiatrists and a psychologist, who concluded he did not require involuntary medication and did not need to be transported, the document said.

The process

The trial will take place at the Delphi Courthouse in Carroll County. But jurors will be chosen from residents of Allen County, more than 100 miles away, which includes Fort Wayne, Allen County Judge Frances Gull ruled last year.

Jury selection begins Monday in Fort Wayne, and once the jury is selected, the case will move to Delphi.

Gull said it made sense to continue the trial in Carroll County, where witnesses and families live, and said the cost of moving the trial would be “extraordinary.”

But she added: “It is painfully clear that it would be impossible to find a jury in Carroll County that would not be involved in this case.”