20 Years After JonBenet Ramsey's Death, Her Father Speaks Out

— -- Nearly 20 years after 6-year-old pageant queen JonBenét Ramsey's death, her father is speaking out in a new documentary on A&E.

“Death would have been a welcomed relief from the pain and agony I felt,” John Ramsey says in the heartbreaking new interview in the documentary, "The Killing of JonBenét: The Truth Uncovered," which premieres tonight.

In the cold case that is still officially open, JonBenét was found strangled to death in the basement of her parent’s upscale home in Boulder, Colorado, the morning after Christmas 1996.

"We have not and will not give up," Boulder Police Department Chief Greg Testa said in a newly released video statement. "We remain focused on this investigation and finding justice for JonBenét."

The case file is bulging with 1,500 pieces of evidence, including 200 DNA samples, and 20,000 tips and leads. Boulder Police interviewed about 1,000 people in 18 states, but are still no closer to catching the killer.

The new two-hour true-crime documentary is promising new revelations, however, and is exploring a theory that an intruder committed the murder.

“The test revealed that mixed with JonBenét’s blood was the DNA of an unknown male,” according to the documentary.

In 2006, authorities thought they had their killer -- a man named John Mark Karr who confessed -- but his DNA did not match, so he was never charged.

JonBenét’s parents, John and Patsy Ramsey, also came under suspicion.

“Mr. Ramsey, did you kill JonBenét?,” ABC News’ Barbara Walters asked the girl’s father back in 2000.

“No, I did not,” he told Walters.

“Mrs. Ramsey, did you kill your daughter?,” Waters then asked JonBenét’s mother.

“No, I did not kill my daughter,” she replied.

Only 12 years after the crime did the Boulder authorities exonerate the family and issue an apology. Patsy Ramsey, however, died in 2006, three years before she and John were exonerated.

John Ramsey remains haunted by his daughter's death.

“We keep our curtains closed. Our doors and windows are locked,” he explains in the new documentary. “Going anywhere is a major organized and planned operation. We get people coming to the door claiming to have information that can be helpful in the case.”

If JonBenét had survived, she’d be 26 years old now.