Shocked that a six-year-old could be dolled up like a pouting adult, the American public long suspected that her affluent parents were responsible for her grisly death.

But a chaotic confession half a world away appeared yesterday to have solved the paedophile murder mystery that has transfixed the American heartlands for a decade — and absolve the parents of blame.

John Mark Karr, 41, an American primary school teacher arrested in Thailand, claimed that he was with JonBenet Ramsey when she was strangled in her Colorado home on Christmas Day in 1996.

Speaking nervously to reporters in Bangkok, the boyish suspect said: “I was with JonBenet when she died. Her death was an accident. I am so very sorry for what happened to JonBenet. It’s very important for me that everyone knows that I love her very much, that her death was unintentional, that it was an accident,” he said.

JonBenet’s body was found in the basement of her 15-room home in Boulder after her mother discovered a handwritten ransom note demanding $118,000 (£65,000). She had been sexually abused and strangled with a garrotte made with half a paintbrush from her mother’s art supplies.

Although it was one of about 800 child murders in America that year, the killing provoked a media sensation with cable news channels repeatedly screening home videos of JonBenet posing coquettishly at child beauty pageants.

For many, the case was a replay of the first 24-hour TV news sensation — the O. J. Simpson murder inquiry of 1994-95 — in which the suspect was acquitted.

JonBenet’s parents, John and Patsy Ramsey, fell under what a prosecutor called the “umbrella of suspicion”. Investigators theorised that Mrs Ramsey, a former beauty queen herself, had killed her daughter in a fit of rage after she wet her bed; or that Mr Ramsey murdered her to cover up sexual abuse.

The couple became popculture symbols of killers who got away with their crime, inspiring episodes of the TV police drama Law & Order, Mad TV and South Park. At one point, police even bugged JonBenet’s grave in the hope of recording their confession.

Mrs Ramsey died of ovarian cancer in June, but she already knew that Mr Karr had emerged as a suspect. He once lived near the Ramseys in Atlanta, where JonBenet was born. The teacher reportedly came under suspicion after e-mailing a journalism professor who made a TV documentary backing the Ramseys’ innocence. He contacted the British academic Michael Tracey, of the University of Colorado, four years ago, the Rocky Mountain News reported.

Ollie Gray, a private investigator who has seen hundreds of e-mails between the two, told the newspaper: “(The suspect) talked about being there, about doing this and doing that — he had a whole bunch of things that didn’t come out before.”

Mr Karr, who has three sons, lost his teaching job in Petaluma, California, scene of the infamous 1993 child murder of Polly Klaas, and was divorced after being charged with possession of child pornography in 2001. He went to work abroad.

Nate Karr, his brother, said he was researching a book on child-killers and it was possible that his inquiries had triggered investigators’ interest. In Bangkok, John Karr said he had written letters to Patsy Ramsey about many things.

Laura Karr, his former wife, said she did not believe that he committed the crime because she was with him at home over Christmas 1996.

Mr Ramsey said yesterday that he had been made aware that Mr Karr was a suspect under surveillance, but he added: “We don’t know with 100 per cent certainty that this is the guy.”

The alibi was one of several questions raised about the arrest. A Thai official said Mr Karr had confessed to drugging and having sex with JonBenet. Toxicology reports found no trace of drugs. Mary Lacy, the Boulder prosecutor, fuelled doubts by hinting that Mr Karr may have been arrested before the inquiry was complete for another reason. He had started work in Bangkok on Tuesday teaching six-year-olds.

Asked what happened when JonBenet died, Mr Karr said: “It’s very painful for me to talk about it.”

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