Delphi murders: John Walsh to spotlight 2017 case in Investigation Discovery show

Since February 2017, residents of Delphi, Indiana, have struggled with grief and uncertainty over the murders of teens Liberty German and Abigail Williams.

Three years have passed — and more than 40,000 tips have been pursued by the Indiana State Police and other law-enforcement agencies — with no arrests.

Now, Investigation Discovery is turning up the heat and asking for the public's assistance to help solve the horrific case. Its show, "In Pursuit with John Walsh," will air an episode on the murders of Libby, 14, and Abby, 13, at 10 p.m. EST on April 1.

According to the TV channel, John Walsh and his son, Callahan Walsh, will ask "In Pursuit" viewers to call into the show with anonymous tips and leads. A news release from the channel said those tips "will be vetted by the appropriate authorities to help bring a killer to justice."

The two girls, who attended the same middle school and were close friends, went for a hike on the Delphi Historic Trails, near the Monon High Bridge, at around 1 p.m. on Feb. 13, 2017, on a warmer-than-normal winter day — a day they had off from school.

Delphi murders of Abby and Libby: What we know about the case

A family member arrived around 3 p.m. to pick the girls up and take them home, but they were nowhere to be found. A short while later, police were notified that Abby and Libby were missing. Later that evening and into the next morning, search parties combed the area around the bridge.

Shortly after noon on Feb. 14, the girls' bodies were found in a wooded area about 50 feet from Deer Creek and a half mile east of the bridge.

Since then, State Police officials have held a handful of news conferences and have released an FBI-generated description of the killer as well as an image and video clip of the man taken from Libby's cellphone. They have not spoken about when the girls died or how they were killed.

They also have provided two police sketches of the man drawn only days apart. But one was released in 2017, just days after the girls' murders, and the other was not released until two years later. They show vastly different-looking men; the earlier-released one shows a man with a mustache and goatee and wearing a hat, who appears to be in his 40s or 50s, and the other depicts a younger man in his 20s or 30s who is clean-shaven and hatless.

An advance clip of an interview between Callahan Walsh and Doug Carter, superintendent of the Indiana State Police, reveals the frustration Carter must be feeling with an investigation that he has repeatedly insisted is not a "cold case."

Police now have placed more emphasis on the sketch showing a younger-looking man, but they haven't completely ruled out the earlier-released sketch of the older man.

Delphi murders: After 3 years with no arrests, police say case isn't cold

"We believe that somewhere between the new sketch and the old sketch is him," Carter says in the interview with Callahan. "He will be somewhere in between those two."

Carter also talked about the importance of the video clip from Libby's phone, which shows a man walking slowly but deliberately across the wooden bridge in the direction of the girls. In the audio clip from Libby's phone that was released by State Police, a voice clearly says, "Guys, down the hill."

"The way a person walks is significant," Carter says in the TV show's interview. "Anybody that knows him knows who it is."

Carter also talked about the audio portion.

"The sound of him telling the girls to go down the hill — somebody knows whose voice that is."

In the portion of the season two finale that will be devoted to the Delphi murders, Investigation Discovery said it will include interviews with Liberty's grandparents, Becky and Mike Patty; Abigail's mother, Anna Williams; and Liberty's sister, Kelsi German, Libby’s sister, who reportedly was the last person to see them alive. It will also include the interview with Carter as well as one with State Police Sgt. John Perrine, who has been heavily involved with the investigation since the start.

John Walsh is well known for his anti-crime activism. He is famous for launching the TV show "America's Most Wanted" in 1988, which he started after his son, Adam, was murdered seven years earlier.

His new TV show urges anyone with information about the case to call 1-833-378-7783 or submit a tip to www.inpursuittips.com.

Police are also still taking tips, and they urge anyone who can help to call the Delphi homicide tip line at 844-459-5786 or send an email to abbyandlibbytip@cacoshrf.com.

A reward being offered in the case by the Indiana State Police Alliance for information leading to an arrest in the slayings. The Delphi Reward Fund amount may be "in excess of $200,000," according to their website.

Call IndyStar digital producer Dwight Adams at 317-444-6532. Follow him on Twitter: @hdwightadams.