JonBenét Ramsey's father says advances in DNA technology can help solve daughter's cold case murder

On the day after Christmas in 1996, John and Patsy Ramsey woke up to discover their 6-year-old daughter, JonBenét, a child beauty queen, was missing from the family's Boulder, Colorado, home.

A handwritten ransom note demanding $118,000 - John's exact bonus that year - was found on the stairs by the kitchen. Seven hours later, John discovered his daughter's lifeless body in a small room in the basement.

The video featured is from a previous report.

For decades, the case has captivated the nation.

Now, 28 years later, John Ramsey remains hopeful that his daughter's killer will be caught. He believes new DNA technology could aid police in re-investigating JonBenét's murder, a case that drew global attention.

JonBenet's autopsy determined she had been sexually assaulted and strangled, and her skull was fractured. Unknown DNA was found under her fingernails and in her underwear.

The Ramseys quickly became suspects, even though no evidence connected them to the crime.

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The Ramseys have consistently claimed they were not involved in JonBenet's murder. However, the Boulder District Attorney's Office took 12 years to fully exonerate the Ramseys and their son, Burke.

As the weeks passed without any arrests in the case, a media frenzy began to build, fueled by nonstop tabloid images of JonBenét competing in beauty pageants.

A number of suspects surfaced, including a man named John Mark Karr, who confessed to the killing in 2006. However, his DNA did not match the evidence, so he was never charged. The case remained open.

To this day, John Ramsey believes his family has a cloud over them because there are still people in the country who believe that he and his late wife Patsy, who died in 2006, are responsible for JonBenét's murder.

"There'd still be 5 to 10% of the population that think, 'yeah yeah it was the father or yeah it was the mother,'" John said.

Despite the loss of his wife and daughter, John Ramsey remains steadfast. He has now remarried and finds comfort in his children and grandchildren.

John is also working with director Joe Berlinger on a new docuseries streaming on Netflix titled, "Cold Case: Who Killed JonBenet Ramsey?"

RELATED: Timeline of JonBenet Ramsey case

"We think the crime can be solved," Berlinger said. "We want to pressure the Boulder police to test DNA."

The docuseries revisits the early stages of the investigation. From the beginning, there were questions about the police's handling of the investigation.

"Early on, they looked into this crazy idea that the parents were responsible," Berlinger said. "They get tunnel vision, so they're not looking to investigate all possibilities."

The crime scene is also under scrutiny, as it was potentially contaminated, which created additional challenges, according to Berlinger.

People were streaming through the house, moving from the kitchen to the living room.

The Boulder Police Department told "Nightline": "We are dedicated to following up on every lead. We continue to collaborate with DNA experts and our law enforcement partners across the country until this tragic case is resolved. This investigation will always remain a priority for the Boulder Police Department."

John Ramsey is confident that advancements in DNA technology can help identify his daughter's killer.

"There's been a number of old, old cold cases solved using this genealogy research," John Ramsey said. "Let's do a reverse family tree and see if he (the killer) had a relative living in Boulder in 1996. That's what we're asking the police to do."