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BOULDER, Colorado (CNN) -- Prosecutors abandoned their case against schoolteacher John Mark Karr on Monday, saying that DNA tests failed to link Karr to the slaying of child beauty contestant JonBenet Ramsey.
Karr was briefly freed from jail but was quickly returned to await extradition to California, where he is wanted on five misdemeanor child pornography counts, Boulder County Sheriff Joseph Pelle said. Karr's extradition hearing is set for Tuesday afternoon.
District Attorney Mary Lacy revealed how the case against Karr was built -- and unraveled -- in a five-page motion asking a judge to drop the arrest warrant that brought Karr from Bangkok, Thailand. (Read the documents -- viewer discretion advised.)
DNA tests completed Saturday confirmed that Karr "was not the source of the DNA found on the underwear of JonBenet Ramsey" -- disproving his claim that he was sexually involved with the child and killed her by accident.
Karr's family also provided "strong circumstantial" evidence he was with them in Georgia at the time of the crime, court papers stated.
The prosecutor's motion said "no evidence has developed, other than his own repeated admissions, to place Mr. Karr at the scene of the crime." (Watch the case against Karr fall apart -- 1:17 )
Karr's Colorado public defender, Seth Temin, first disclosed that no charges would be filed and that a hearing scheduled for late Monday afternoon had been canceled.
"We're deeply distressed by the fact they took this man, dragged him back here from Bangkok, Thailand, with no forensic evidence confirming the allegations against him and no independent factors leading to a presumption that he did anything wrong," Temin said.
Prosecutors said in Monday's motion that "there was a great risk that [Karr] might disappear if he became aware that people from his past were being interviewed about his admissions."
"Until Mr. Karr was identified, there was no way to try to confirm or disprove his admissions," they said.
Prosecutors said they also feared Karr could be a danger because he had expressed "sexual interest in specific young girls" at a Thai school where he had taken a job as a teacher.
According to Lacy's court papers, University of Colorado journalism professor Michael Tracey brought Karr to the attention of investigators in April.
Using the pseudonyms "D" and later, "Daxis," Karr began communicating in 2002 with the professor, who has produced documentaries on the 10-year Ramsey investigation.
At first, court papers say, "Daxis" claimed to know two people who participated in the crime, but later insisted he was personally responsible.
His story emerged slowly, through e-mails, a manuscript and nearly a dozen phone calls. Still, the writer continued to keep his true identity and whereabouts secret from Tracey, the court papers stated.
He claimed to be sexually involved with the child, including "temporarily asphyxiating her," the court papers said.
'Lost track of time'
And, he said he "had 'accidentally' killed her by becoming so sexually involved that he lost track of time so that the asphyxiation lasted longer than he intended, causing her severe injury and leading him to inflict a severe blow to her head," the document stated.
Autopsy results showed JonBenet had suffered a blow to the head and been strangled with a garrote tightened with a paintbrush handle.
Tracey reached out to authorities in April when his contact became increasingly interested in contacting Patsy Ramsey, JonBenet's mother, who was in the final weeks of her life. Patsy Ramsey died of ovarian cancer in June. The contact also related that he was in continuing contact with young girls, the court papers stated.
At one point, in an effort to locate Karr, investigators got Tracey to persuade him to call JonBenet's parents. "Law enforcement agencies cooperated in an unsuccessful effort to trace that call," prosecutors said Monday in their motion. The date of the call was not disclosed.
Authorities were eventually able to trace phone calls to Tracey from "Daxis" to Karr in Thailand, court papers said.
In a court filing last week, Boulder prosecutors said they had known Karr's identity for just five days before he was arrested and that the investigation into his possible role in the case was in its preliminary phase.
After his arrest, Karr told reporters in Thailand he was with JonBenet the night she died, and that her death was an accident. The 6-year-old's beaten and strangled body was found December 26, 1996, in the basement of her family's Boulder home.
Karr's arrest, nearly 10 years after the grisly crime that grew into an international media sensation, had given the Ramsey family hope that the slaying had, at long last, been solved.
"It's another bump in the road for us emotionally, but I think we saw Lady Justice put her gavel down today," Pam Paugh, Patsy Ramsey's sister, told CNN. "I don't think that this story is over yet, and I think, again, patience is the prudent thing to desire at this point."
John Mark Karr is shown at a hearing in Los Angeles at which he agreed to waive extraditon.