A LANDMARK cyber-bullying trial is underway with prosecutors accusing a 49-year-old mother of sending taunting emails to a vulnerable teenage girl who later killed herself.

Missouri woman Lori Drew faces US federal charges of computer fraud and conspiracy in Los Angeles in connection with the tragic death of 13-year-old Megan Meier, who committed suicide in 2006 at her home in St Louis.

Ms Drew, her daughter and a family friend who are not on trial, posed as a fictitious 16-year-old boy named "Josh Evans" who befriended Megan on social networking site Myspace as part of a plot to seek revenge.
 
Megan, who Ms Drew suspected of spreading false rumors about her daughter, hanged herself after receiving a message from "Josh" which said the world would be a better place without her, according to court documents.

The case is the first criminal prosecution in US legal history relating to allegations of cyber-bullying.

Federal attorney Thomas O`Brien told a six-man, six-woman jury that Ms Drew targeted Megan even though she knew the teenager was vulnerable.
 
"The defendant knew Megan Meier was depressed, suicidal and boy-crazy,"  said Mr O`Brien at a US District Court in California.

Ms  Drew set out `to tease, embarrass, humiliate, make fun of and hurt her," he said.

However Ms Drew`s defense attorney Dean Steward stressed in opening remarks his client was not charged with Megan`s death.
 
"This is a computer fraud and abuse case ... not a homicide case," the defense attorney said.

"This was a deeply tragic case for everybody -- most of all for Megan Meier."

Mr Steward told jurors his client was not responsible for the email from ``Josh`` in which Meier was told the world would be a better place without her.

Prosecutors in Missouri declined to bring a case against Ms Drew, who is being tried in California because on a felony conspiracy charge and three counts of illegally accessing protected computers without authorisation.

The case is being prosecuted in Los Angeles because Fox Interactive, the owner of MySpace, is based in Beverly Hills.

Ms Drew faces illegal access charges on the basis she lied on the fake MySpace profile created to taunt Megan, violating the site`s terms of service which requires users to provide "truthful and accurate" registration information.

Each count carries a maximum five-year jail term.

MySpace and Fox Interactive are owned by the parent company of the publisher of news.com.au.