A private investigator claims a blue backpack carried by Cherrie Mahan at the time of her disappearance 40 years ago from a Winfield school bus stop could be key to cracking the case.

“I am convinced through some fairly recent testimony and input that Cherrie’s book bag was very likely submerged in a pond in an area very near her grandmother’s home,” said Iowa-based private eye Steve Ridge at a Tuesday news conference in Summit Township. “That’s one hell of a lead.”

The 8-year-old’s bag has not been a major focus for investigators, at least publicly.

Cherrie’s mother, Janice McKinney, and a team of friends known as Cherrie’s Angles previously identified a 26-acre parcel across from where the girl’s grandmother lived in Clinton Township as an area of interest.

Ridge, who is licensed as a private investigator in other states but not in Pennsylvania, said its possible the bag is no longer in the pond. Rather than looking for the bag themselves, he urged the public to submit tips to him, Cherrie’s Angels or state police, who are leading the official investigation.

State police were invited to but not present at Tuesday’s event.

Cpl. Max DeLuca, the lead investigator in the case, declined to comment on the bag or its significance.

“I’ve looked into a lot of different things,” he said. “I’m not going to comment on specifically what we looked into.”

Since taking the case pro bono almost three months ago, Ridge has pored over public documents (he cannot access police files without a license), visited the site of Cherrie’s disappearance and put up a $100,000 reward for the location and positive identification of the girl’s remains.

In his experience, “a no body, circumstantial evidence case is just very hard to prove,” making the remains crucial to a conviction.

Ridge, who worked as a broadcast news reporter before amassing a small fortune as a media executive, has posted $100,000 and $50,000 rewards in the disappearances of Iowa news anchor Jodi Huisentruit and Kansas mother Angela Green, respectively.

He also has contributed his skills as an investigator. In late March, Ridge and his attorneys persuaded a judge to unseal parts of a 2017 search warrant in the Huisentruit case, including GPS data for vehicles owned by a person of interest, according to a Mason City Globe Gazette news story.

Furthermore, he claims to be the only person who ever got the person of interest to discuss the case.

With help from assistants and interns, Ridge also uses artificial intelligence to extract patterns from interviews and other files, creating something of a digital “cork and yarn” evidence board.

Other technological advancements, like accessible genetic testing and social media, have helped progress dead-end cases in other parts of the country. In California, for instance, an AncestryDNA test led an elderly man to learn he was kidnapped in 1951.

In Cherrie’s case, McKinney and company have repeatedly asserted their belief she was abducted by someone she knew, sexually abused and killed. This theory has been endorsed by Ridge and Ken Mains, another private investigator who recently visited rural Winfield.

Mains has since posted two YouTube videos breaking down the case and directing attention to a blue compact car observed at the bus stop where Cherrie vanished on Feb. 22, 1985. He referred to a van with a mural of a skier, which was also seen in the area, as a “red herring.”

Those close to the case have hinted at knowing who did it.

On Tuesday, Cherrie’s Angels co-leader Bailey Gizienski gave the clearest picture yet of who that might be: a man imprisoned on child molestation charges.

State police do not have a prime suspect or specific areas where they believe Cherrie is buried.

“I don’t know how (Ridge has) narrowed his scope to one person,” DeLuca said.

McKinney, 64, who was visibly emotional throughout the news conference, emphasized the toll this case has taken on her over the years, even as recent developments have left her feeling closer to answers than ever.

But, she added, “I have never ever given up hope.”