For years, John Mark Karr had been begging to get caught for a crime, it seems, he did not commit.
"This guy confessed on numerous occasions in great detail," said Peter Maguire, a deputy district attorney in a Boulder, Colo., at a news conference Tuesday. "He confessed in e-mails. He confessed in telephone conversations. … He admitted it to a police officer."
Karr even confessed on international TV, telling the world that he was with JonBenet Ramsey when she died, a claim he had been making to University of Colorado journalism professor Michael Tracey for years.
It took more than 400 pages of e-mails for Karr to be arrested in connection with the murder of JonBenet, but it seems it only took three letters to get him off the hook: D-N-A.
Karr's did not match that found in JonBenet's clothing. Boulder District Attorney Mary Lacy said she would not charge him in the case, citing lack of evidence.
While people wonder why Karr was willing to take the heat, experts think he may sincerely believe he deserves it.
It was a stunning end to the latest chapter in a case that for years had engrossed the nation and the world.
The biggest question: "Why?"
Why would Karr confess to murdering the 6-year-old if he was not guilty?
In a news conference Tuesday, Lacy said the reason was simple: Karr "sincerely believes he killed JonBenet Ramsey."
In chilling, explicit detail, Karr recounted to Tracey exactly how he believed he had killed JonBenet on Dec. 26, 1996, providing minutiae about the murder not widely known.
"I have basically confessed at her grave," Karr wrote. "I talk to her out loud. … I was saying things to her like 'oh my God, I'm so sorry.'"
He even said why he supposedly chose Christmastime.
"I am very sentimental," Karr wrote on June 5. "I like special nights and it was a special night. … it was Christmas night."
Michael Welner, a leading forensic psychiatrist, told ABC News that he believed Karr had confessed because he wanted acknowledgement as someone who was close to JonBenet.
"By confessing to being the last person to see JonBenet Ramsey alive, he is able to establish a relationship that no one has," Welner said. "He has a special relationship that no one can understand, and it's a permanent relationship that even in death John Karr wanted to hold on to, in fantasy."
Welner said Karr's e-mails and phone calls revealed a deeply delusional man desperate for human attention.
He also cautioned that Karr's motives might have changed over time, as he became more and more caught up in his fantasy world.
"From what we know about John Karr, this started with him seeking acknowledgment by being attached to JonBenet in her last moments, and it ended with him seeking much more than acknowledgement. Perhaps fame," Welner said.
Lawyers from several high profile cases told ABC News that they had encountered many false confessions in their cases.
Even in Boulder, Lacy said that, over the years, dozens of people had confessed to killing JonBenet.
Karr's fantasies went beyond a detailed confession, though. They included visions of grandeur.
He had already picked out the movie star who would play him in a film.
In phone conversations with Tracey, Karr expressed a desire to have Johnny Depp play him in a film version of his life.
"He even looks like me," Karr said of Depp, adding he was sure the star would choose to take on the role.
Karr also sent a detailed manuscript to Tracey about his relationship with JonBenet, insisting that he would have to maintain strict control over the movie rights.
Karr remained in custody in a Boulder jail Tuesday night, awaiting extradition to California where he will face child pornography charges.
Welner said Karr was an extremely rare case, because he had confessed not as a result of an interrogation or suggestion by police but on his own.
Welner said there was another unusual aspect to Karr's confession.
"A pedophile has a sexual fantasy and attraction to children. John Karr has sexual fantasy and attraction to children, but he became obsessed with celebrity victims -- people he didn't have an attachment to or a connection to."
Karr seemed determined that he would be known for his involvement in JonBenet's death, or at least in the Ramsey saga.
He told Tracey: "I love JonBenet … 'til this day I love her and I've loved her very much and I … played an unreal role in her life and her death (whispered)."
Less than two weeks after the world witnessed Karr's very public confession in Thailand, it seems like it was only a role, and one that was only real to Karr.
"It doesn't surprise me that a human being can develop a false belief or a false memory, and truly believe they did something they didn't do," psychologist Elizabeth Loftus said to ABC News.
She said that Karr could believe it so strongly and that he would pass a standard polygraph test.
"If he truly believes that he did this, then he would be able to pass a lie detector test," Loftus said. "Because the lie detection -- if in fact you believe in it -- measures the stress of a deliberate fabrication. … What we may have here is an honest liar."
Dr. Welner is chairman and founder of the Forensic Panel (www.forensicpanel.com), a forensic consulting group that provides peer-reviewed expert testimony in court cases. He is also developing an evidence-based test to assist criminal sentencing called the Depravity Scale, http://depravityscale.org, which invites Americans to participate in surveys that are used to form a legal standard of what represents the worst of crimes.