The rape and murder of an 11-year-old Illinois babysitter has gone unsolved for three decades, but police say there is reason for hope that the perpetrator will be caught, WFLD-TV reports.

Holly Staker was babysitting two children on the evening of August 17, 1992, in the Chicago suburb of Waukegan when an intruder entered the apartment.

Staker was raped and brutally stabbed to death, and authorities initially thought they found the alleged attacker: Juan Rivera.

Prosecutors charged Rivera three times in connection with the case, but his conviction was overturned on appeal, with appellate courts finding that police manipulated him into confessing, according to the Chicago Tribune.

Rivera spent more than 19 years in prison before being exonerated and receiving $20 million as part of a settlement for the wrongful conviction. It is reportedly the largest such settlement in U.S. history.

Then in 2014, investigators determined that DNA material linked to a 2000 murder in North Chicago matched DNA evidence from Staker’s case.

But authorities have not determined whose DNA it is. Police have entered the genetic profile from the DNA into various databases of convicts but no matches were found, the Tribune reports.

It is not clear if investigators have tried using familial DNA searches, which can be used to find a suspect’s relatives who have shared their DNA profile to commercial genealogy services—the method used to catch the Golden State Killer.

Waukegan Police Chief Keith Zupec told WFLD-TV that his department continues to investigate Staker’s case and has a potentially useful lead.

“It’s not as simple of a lead as ‘hey, this is who did it,’” Zupec told the television station. “It’s a little more complicated lead that we are working . . . but a very strong viable lead.”

Zupec, who before serving as chief led the investigation into Staker’s killing, said the department still gets inquiries and tips about the case.

“We receive calls or we receive letters from people. That’s not uncommon for us, several times a year that we receive some tip in this case,” Zupec told WFLD-TV.

He added: “We’re going to do everything we can. Just because this case is 30 years old does not mean that it’s not a case we intend to resolve.”

To report information about the Staker case, call the Waukegan Police Department at 847-360-9000 or Lake County Crime Stoppers at 847-662-2222.

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