A day after the case against Karr was dropped, District Attorney Mary Lacy and her team defended their decision to bring him to Colorado from halfway around the world on a jumbo jet, with champagne and pate for dinner.
Ms Lacy said it was difficult to be sure about any suspect's claims because every bit of physical evidence in the case had been disclosed to the public in the past 10 years.
"This guy confessed on numerous occasions in great deal," said Peter Maguire, a deputy district attorney.
"He confessed in emails, he confessed in telephone conversations ... he admitted it to a police officer. This was a bizarre crime and the person who committed this crime acted in a bizarre way."
JonBenet's father found the little girl's body in the basement of their Boulder home on Boxing Day 1996. For years, suspicion has focused on either an intruder or the girl's parents, John and Patsy Ramsey.
Karr, who in emails and telephone conversations expressed a fascination with JonBenet and Polly Klaas, a murdered California girl, said after his arrest in Thailand this month that he was with JonBenet at the time of her slaying, which he called an accident.
Emails reveal extent of delusions
The extent of Karr's delusions about the child beauty queen's murder became clearer when Colorado authorities released emails and recordings of phone calls he had made about the case.
Karr once described himself as the "dashing prince" who was with JonBenet when she was killed and believed Johnny Depp should play him in a movie about the murder.
He said he had written a screenplay about the murder and said the movie would make $US1 billion ($A1.31 billion).
Prosecutors released the material to show why they considered Karr a viable suspect in the JonBenet slaying.
The emails and recorded phone calls were to University of Colorado journalism Professor Michael Tracey who has worked on documentaries about the JonBenet case.
DNA tests did not match Karr to material found on the girl's body.
Prosecutors suggested in court papers that Karr was just a man with a twisted obsession who confessed to a crime he did not commit.
Ms Lacy has been sharply criticised for detaining and arresting Karr.
Republican Governor Bill Owens said Ms Lacy, a Democrat, "should be held accountable for the most extravagant and expensive DNA test in Colorado history".
"The decisions were mine," Lacy said on Monday. "The responsibility is mine and I should be held accountable for all decisions in this case."
Karr made some "pretty bizarre" claims in hundreds of pages of email conversations with a Colorado professor, who alerted authorities to Karr's claims, Ms Lacy said.
But she conceded that authorities were not able to confirm that Karr was in Boulder at the time of the slaying.
Karr is being held at the Boulder jail until he can be sent to Sonoma County, California, to face child pornography charges dating to 2001. An extradition hearing is scheduled for Monday.