The Clue in JonBenét Ramsey's Autopsy That Makes a Case Expert Suspicious: 'Someone Isn't Being Truthful'

The battered, lifeless body of JonBenét Ramsey was discovered in the basement of her family’s Boulder, Colorado, mansion on Christmas Day, 1996 – and the case has confounded investigators and case experts ever since.

That includes Steven Pitt, a nationally recognized forensic psychiatrist in Arizona who worked on the investigation. And he says there is a single piece of evidence from the case that is key for him:

A piece of fruit – specifically, a pineapple.

In this week’s issue, PEOPLE takes a new look at the evidence in the case, as well as the suspects and the questions that endure nearly two decades after JonBenét’s killing. Pitt says the 6-year-old’s autopsy showed there was pineapple in her digestive tract, suggesting the fruit hadn’t had time to fully digest before she was killed.

But Pitt says Patsy Ramsey, JonBenét’s mother, told investigators her daughter hadn’t had any of the tropical fruit in the hours before her disappearance.

To read more about the latest in the JonBenét investigation, pick up this week’s issue of PEOPLE on newsstands Friday.

“The fingerprints on the bowl or cup that were used to give JonBenét the pineapple were Patsy’s fingerprints,” Pitt tells PEOPLE. “It suggests someone is not telling the truth about what happened at that home that night.”

(JonBenét’s parents have never been charged in the case and have maintained their innocence.)

WATCH: 5 Clues That Could Reveal What Really Happened To JonBenét Ramsey

Pitt says he doesn’t think there will ever be justice for the 6-year-old pageant contestant – despite the hundreds of pieces of evidence and thousands of pages of investigative documents, and despite what he calls underrated work from detectives at the time.

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“It has been solved,” Pitt tells PEOPLE. “I think in the minds of lots of people, the case is solved. The question is, Do I think anyone will ever be criminally charged? No.”

• Reporting by VICKIE BANE