It has been nearly three decades since 6-year-old JonBenet Ramsey was found murdered in her Boulder, Colorado, home on the day after Christmas in 1996, yet the high-profile case remains unsolved.

One alleged reason the case still hasn't been solved is that several pieces of DNA evidence in the custody of the Boulder Police Department have never been tested, according to the slain girl's father, John Ramsey, NewsNation reported.

The father, who has pressed the police for answers for years, is now urging them to make use of new technologies and expansive DNA databases in hopes of finally identifying his daughter's killer.

Police should use new DNA testing technology, expanded databases

"Technology’s advanced so far. For this to be really evaluated correctly, it needs to go to an outside lab," Ramsey told NewsNation's Ashleigh Banfield of the alleged DNA samples held by the police. "The technology is there. They’re willing to do it. They have to be asked by the police to do it."

In addition to making use of advanced DNA testing technology, Ramsey also wants the police to expand the search for a match beyond just the FBI's database of criminal DNA samples.

"That’s a database of felons … people that have done bad things. It’s not that big of a database," Ramsey said. "The public database is hundreds of millions of samples. That’s the database they need to go to."

"Work back and find the relative of a near-match that was living in Boulder, Colorado, in 1997. That, we believe, is our best hope of finding the killer," he added.

More testing needed

Ramsey also made his plea for more DNA testing in a recent interview with True Crime News and said of the Boulder Police Department, "We're not asking you to clear us, to apologize, or be nice to us again -- just do the things that you should do that can be done. If you do that and we don't get an answer -- we tried. We did everything we could do."

The father, along with his wife and their son, were initially viewed as suspects in JonBenet's horrific murder, but were eventually cleared of suspicion by authorities. Ramsey claims that there is "unidentified male DNA" recovered from the scene of the crime -- along with other items containing unknown DNA, including the alleged murder weapon -- that has, to his knowledge, never been tested.

"If you're not going to turn over authority of the case, at least turn the evidence over to the FBI, let them play with it, do what they can do. But don't just keep it locked in a file drawer," he said of the police.

New chief provides hope case will be solved

Fox News reported that Ramsey, who has butted heads with the Boulder PD for decades over his daughter's cold case, has some optimism that the investigation may be reopened and scrutinized again under a new police chief, the sixth one he has dealt with since the murder occurred.

He praised Chief Stephen Redfearn as a "good" and "competent fellow" and said that it was "good news" that he'd been hired "from outside the system" instead of "promoted from within," given his contentious history with the department that initially sought to pin the murder on him and the family and has since allegedly sat on alleged evidence.

The outlet noted that the purportedly untested evidence includes the garote used to strangle JonBenet, a ransom note found in the kitchen, a suitcase found near a basement window, and an unknown flashlight and rope found in other parts of the house, among other things.

"We have an unidentified male DNA result from the testing they did in 1997, which … by today's standards, it was primitive," Ramsey said. "But we have an unidentified male DNA sample, which was reported to the police in January 1997. They kept that a secret because it conflicted with their conclusion that we were guilty. How do we explain that away? Which they tried desperately to do."