JonBenét Ramsey's father speaks out on DNA test 'that could solve cold case' 28 years on from brutal murder

JonBenét Ramsey's father still hasn't given up on his six-year-old daughter's murder case, 28 years on.

On December 26, 1996, John and Patsy Ramsey woke up to find a chilling ransom note detailing that their youngest daughter had been kidnapped.

Instead, the little girl was sexually assaulted and murdered in her own home in Boulder, Colorado, US.

Netflix's new three part documentary Cold Case: Who Killed Jonbenét Ramsey, will explore the unsolved case. Watch below:

JonBenét's family were the police's most likely suspects in her brutal murder, and the case became a national obsession.

While the investigators explored various intruder theories, they struggled with contaminated evidence.

The unsolved case has fuelled countless theories and questions over the roles of family members. DNA tests rule out a popular theory that the family's eldest son, Burke, accidentally killed his sister.

In 2008, the tests suggested that an 'unexplained third party' was involved.

John, the girl's father, has today (21 November) called for police to be more open to using outside resources.

New Netflix documentary Cold Case: Who Killed Jonbenét Ramsey will explore one of the most publicised cases in recent times (YouTube/Inside Edition)

"There's been some horrible failures in that space for the last 25 years," he told NBC's Today.

"Hopefully there's someone who knows something that would come forward, so we want to keep the case alive and in front of people. I believe it can be solved if the police accept help from outside their system, that's been the flaw for 25 years.

"For 25 years, the police department was contained, very poor leadership. Which is tragic, they had no experience.

"The fellow investigating our case for 25 years was an auto theft investigator before he took the case over. It was a roadblock."

He continued: "They wouldn't accept help from the outside. We are hopeful now with the new police chief that he will exercise good leadership and accept help.

"To my knowledge they have not worked with federal agencies, and there has been so much offered.

The girl was sexually assaulted and murdered in her own home (Netflix)

"I won't give up pressing the authorities to do their job until I see that they do their job. And that's been the frustration for 25 years."

Ahead of the Netflix true crime doc, which releases on Monday (25 November), Director Joe Berlinger said: "This case can be solved. DNA technology was very different back then, the DNA was flawed.

"Old items that were tested need to be retested. The one good DNA sample that we have is a mixture of Jonbenet's DNA and a foreign male's DNA.

"There is now technology where those samples can be separated. I don't understand this institutional intransigence to solving a case, [the police] need help."