Just a week and a half after Karr's arrest in Thailand was seen as a remarkable break in the sensational, decade-old case, prosecutors suggested in court papers that he was just a man with a twisted fascination with JonBenet who confessed to a crime he didn't commit.
"The people would not be able to establish that Mr. Karr committed this crime despite his repeated insistence that he did," District Attorney Mary Lacy said in court papers.
CBS News Denver affiliate KCNC's Rick Sallinger reports that hair and saliva taken from Karr in Boulder after his arrival last week were tested over the weekend at the Denver police crime lab and that he was ruled out as the source of the DNA taken from the crime scene.
The 41-year-old schoolteacher will be kept in jail in Boulder until he can be sent to Sonoma County, Calif., to face child pornography charges dating to 2001. An extradition hearing was scheduled for Tuesday.
The district attorney vowed to keep pursuing leads in JonBenet's death: "This case is not closed."
Karr was never formally charged in the slaying. In court papers, Lacy defended the decision to arrest him and bring him back to the United States for further investigation, saying he might have otherwise fled and may have been targeting children in Thailand as well.
CBS News legal analyst Andrew Cohen says because officials were worried Karr would bail if they tried to get DNA tests in Thailand, they figured they'd better get him back to the U.S. and do the tests.
"The problem with doing that is you don't have a strong physical case and it's a red hot media blitz and everybody creates these large expectations for what this guy is or isn't," Cohen says. "It's a huge embarrassment for Boulder."
Lacy said Karr emerged as a suspect in April after he spent several years exchanging e-mails and later telephone calls with a University of Colorado journalism professor who had produced documentaries on the Ramsey case.
According to court papers, Karr told the professor he accidentally killed JonBenet during sex and that he tasted her blood after he injured her vaginally. But the Denver crime lab conducted DNA tests last Friday on a cheek swab taken from Karr and were unable to connect him to the crime.
"This information is critical because ... if Mr. Karr's account of his sexual involvement with the victim were accurate, it would have been highly likely that his saliva would have been mixed with the blood in the underwear," Lacy said in court papers.
She also said authorities found no evidence Karr was in Boulder at the time of the slaying. She said Karr's family provided "strong circumstantial support" for their belief that he was with them in Georgia, celebrating the Christmas holidays. JonBenet was found beaten and strangled at her Boulder home on Dec. 26, 1996.
Defense attorney Seth Temin expressed outrage that Karr was even arrested.
"We're deeply distressed by the fact that they took this man and dragged him here from Bangkok, Thailand, with no forensic evidence confirming the allegations against him and no independent factors leading to a presumption he did anything wrong," Temin said.
In an interview Monday with MSNBC, Gary Harris, who had been spokesman for the Karr family, said he knew the DNA would not match.
Karr has been "obsessed with this case for a long time. He may have some personality problems, but he's not a killer," Harris said. "He obsesses. He wanted to be a rock star one time. ... He's a dreamer. He's the kind of guy who wants to be famous."
Earlier this month, Ramsey family attorney Lin Wood pronounced Karr's arrest vindication for JonBenet's parents, John and Patsy Ramsey, who had long been suspected in the killing.
On Monday, the attorney said: "From day one, John Ramsey publicly stated that he did not want the public or the media to jump to judgment. He did not want the public or the media to engage in speculation, that he wanted the justice system to take its course."
Wood said he still has great confidence in the district attorney. Patsy Ramsey died of cancer in June.
JonBenet Ramsey's aunt, Pamela Paugh, said she was disappointed there won't be a prosecution of someone in the case, but added: "I think our justice system worked as it was supposed to."
"We asked the DA to do her thing. She did it," said Paugh, who is Patsy Ramsey's sister. "My disappointment came about the end of December 1996 when we didn't have the killer then. We've had 9½ years of disappointment and waiting."
Nate Karr, John Karr's brother, said he was elated by the news. "We're just going to be celebrating with family," he said.
Colorado Gov. Bill Owens blasted prosecutors for wasting thousands of taxpayer dollars to bring Karr to Colorado given such a lack of evidence. The district attorney "should be held accountable for the most extravagant and expensive DNA test in Colorado history," he said.
Scott Robinson, a Denver attorney who has followed the case from the beginning, said prosecutors may now be back at square one in the JonBenet case. He said Karr may be charged with lying about his role in the case.
"Seems to me there should be some criminal consequences," he said. "He has cost the taxpayers an enormous amount of money."
Karr was arrested in Petaluma, Calif., in 2001 on charges of possessing child pornography but fled before he could be tried. Colorado authorities said that after the Boulder case against Karr was dropped, California officials asked that he be turned over to them for prosecution.
In court papers, prosecutors said Karr began exchanging e-mails with professor Michael Tracey in 2002, signing them "D" and later "Daxis." The meaning of "Daxis" was not immediately clear.
At first, Karr seemed to be just someone with an intense interest in the case, but he soon claimed responsibility for the crime, and provided more and more detail about that night, according to court papers. He claimed that he accidentally killed JonBenet during sexual activity that included temporarily asphyxiating her, prosecutors said.
He began telling his story in hopes of being included in a book Tracey was planning to publish, according to the court papers. Authorities eventually traced his calls and identified Daxis as Karr, prosecutors said.
"Are you asking me why I killed JonBenet? I don't see it that way," Karr wrote in a May 22 e-mail. "Her and I were engaging in a romantic and very sexual interaction. It went bad and it was my fault."
The DA's office late Monday provided hours of discussion and pages of grisly details from Karr's correspondence with professor Michael Tracey, who alerted authorities.
Karr described how he hung JonBenet with a rope and slowly strangled her to put her in a "dream-like state" before performing oral sex. He said he tasted her blood after the sex went too far and tried to revive her when he realized she was dead.
"I loved her so much and I am so sorry that she died in my arms," Karr wrote to the professor in May. "If anyone came close to screaming, it was I. ... 'Please don't leave me. I love you so much. Oh, babydoll, please come back to me!"'
During a July 15 telephone call with Tracey that lasted 100 minutes, Karr — going by the alias Daxis — said he placed a new "necklace around the throat of the child." The garrote was loosened and tightened, and JonBenet stopped breathing.
"Daxis explained again that due to the twitching of JonBenet he was concerned she might be brain dead but her body could continue to survive," according to a summary of the call in the 98-page arrest affidavit. "He did not want JonBenet to suffer, so he struck her in the head with a flashlight he brought with him."
The district attorney said there was no way to take a cheek swab from Karr without alerting him that he was under investigation, and that would have created an "unacceptable risk that he would flee."
Also, Karr was about to start a teaching job in Thailand, and in his correspondence began to describe an interest in several girls "in much the same terms that he had described his interest in JonBenet," Lacy said in court papers.
In a July 19 e-mail, Karr described feeling excited to have two 5-year-olds "flashing their hot little bellybuttons at me" and later how a "naked little foot felt so sexy in my hand."
Authorities confirmed he was involved with at least one of the girls, Lacy said.