In any case, Megan's mother, Tina Meier, said there was nothing to suggest her daughter would have taken her own life. But an internet "romance" with a boy called Josh Evans changed all that. Josh was supposed to be 16, and he charmed Megan through her MySpace website. They never spoke, since Josh said his parents did not have a phone. Josh was, however, a fiction, an invention of Drew, a neighbour of the Meiers in Dardenne Plains, Missouri.

Drew created Josh to try to find out what Megan was saying about Drew's daughter. At one time, Lori and Curt Drew's daughter and Megan were best friends, but they drifted apart, and when Megan changed schools she ended the friendship. Lori Drew had told a neighbourhood girl about the hoax, and the girl's mother, who asked for anonymity, said that "Lori laughed about it", adding that she would "mess with Megan". Soon after Josh insulted and turned on Megan, she killed herself. Law enforcement authorities warn that older children and teenagers tend to be most at risk from internet predators because they are less likely to be supervised. They are also more open to discussing personal issues and relationships, although the predators police have in mind are probably nothing like Lori Drew.

A child and school psychologist, Laurie Zelinger, said the internet was intensifying pressures on adolescents. They were particularly susceptible to peer pressure and peer acceptance as part of becoming independent. "We know that kids are so desperate to be accepted that they will violate their own rules. They need to experience affiliation, and a sense of belonging will lead children to engage in behaviours that are counter to family values and even their own sense of conscience.

"Before the internet, all of this happened in school hours. They would pass notes in class, have sorts of sign language, use the telephone when they reached home … now neighbourhoods are more spread out, people are living in large homes, children tend to maintain contact through the internet and text messaging. They can have this contact 24/7. It's magnifying an issue that's always existed." Zelinger said that understanding adolescent behaviour meant understanding how their brains develop, which is in a predictable pattern from back to front. The cerebellum, located in the back, houses the amydala, which is the seat of emotion. As such, adolescents often experience rage and fear, since that area is among the first areas to develop. The front part of the brain, the last to develop, controls decision-making, interpreting emotions and executive decisions, rendering teens biologically incapable of making mature decisions in some contexts. Between the ages of 12 and 16, the prefrontal cortex also shows decreased grey matter, thereby further limiting the capability of the child to make sound decisions.

Then puberty rushes in, bringing an onslaught of hormones seeking excitement and arousal. This combination of late front brain development, with its poor decision-making skills, and hormonal influences, often leads to risk-taking behaviour and intense emotional involvement. Teens can thus be easily influenced, intensely reactive and especially vulnerable to the opinions of peers.

Megan Meier had tried desperately to join the popular crowd at her school, only to be teased about her weight, her mother told The New York Times. At the beginning of eighth grade last year, she transferred to a nearby Catholic school and soon had a new group of friends, lost 9 kilograms and joined the volleyball team. Because Megan had been on holiday with the Drews, Lori Drew knew she had been prescribed antidepressant medication and that she had a MySpace page. As "Josh", Drew contacted Megan through her web page. For Megan, the online relationship sparkled until one day Josh turned on her and sent a message that read: "I don't like the way you treat your friends, and I don't know if I want to be friends with you." He also said she was "fat" and "a slut". They argued online for an hour and other girls who had linked to Josh's website added abusive messages to Megan.

On October 16, last year, Josh sent his final message, telling Megan the world "would be a better place" without her. Soon afterwards, Tina Meier found her daughter hanging from a cloth cord. As the crisis unfolded, Lori Drew reportedly rang the neighbourhood girl in whom she had confided, telling her to "keep her mouth shut". She did. Lori and Curt Drew attended Megan's funeral and wake; they even asked the Meiers to hide their children's Christmas presents in the garage. Weeks later the neighbour who sought anonymity told Megan's parents the truth about Josh. "I felt like such a fool," Ron Meier told The New York Times. "I'm supposed to protect my family, and here I allowed these people to inject themselves into our lives."

He smashed the Christmas presents, and it was when the Drews complained to police about the damage that Lori Drew's explanation for her role in Megan's death became clear. Tina Meier said no words could explain her rage: "These people were supposed to be our friends." An practitioner of internet law, Parry Aftab, says "Josh's" attack on Megan was compounded when girls who knew Megan joined in, creating a mass cyber-bullying episode. "Everyone says Megan had a crush on a boy and it broke up and she killed herself. This was a lot more than that," Aftab says. She said girls who read Josh's comments joined in the attack. Aftab says bullying comprises 80 per cent of complaints to social networking sites.

"Cyber bullying follows you everywhere. It will follow you home and to grandma's. You can't avoid it by leaving the schoolyard and you never know if it's your best friend or your worst enemy," she says. "Sixty per cent of cyber-bullying is anonymous, and best friends know your secrets and your passwords." Children need to be taught to use privacy settings to protect themselves and their identity. They should not share passwords to their sites, and they should admit only friends to them. They should be also prepared to change passwords, not choosing obvious ones that others could easily guess.

Parents are be advised to check their children's sites to ensure material immediately accessible does not put their children at risk, Aftab says. Information they may not want parents or teachers to see should be guarded from public view, and parents should insist on seeing their children's network pages "tomorrow". "It's important parents don't overreact and give their kids time to prepare the site for them to see," she says. The Meiers lived secretly with their knowledge of Drew's involvement for a year while the FBI investigated the case, but no charges have been laid. A police spokesman says Drew's behaviour might have been rude and immature but it was not a crime. The internet may be new-era technology, but in the absence of legal action against Lori Drew it has triggered a round of old-style retribution.

Drew's address and phone number have been widely publicised on websites and blogs drawn to Megan Meier's tragedy, along with calls for a boycott of the Drew family company. Neighbours have shunned the Drew family, who still live four doors from where Megan took her life. The Meiers have moved out. Aftab, who is working with Tina Meier on developing coping resources for children, confirmed Tina and Ron Meier have separated. Ron lives in fear that if something happens to the Drews, he will be a prime suspect.

The case has raised talk of legislation against internet harassment, but the young will remain at risk. Zelinger says hormonal and developmental changes mean adolescents are a vulnerable, impulsive group that seeks increasing peer contact. "I think the internet brings more of this. It leaves a printable account for a child to read over and over again," she says. "It's something for them to ruminate over. They can become preoccupied." With The New York Times/The Seattle Times