Teenager Luke Mitchell has been found guilty at the High Court in Edinburgh of murdering his girlfriend Jodi Jones.
The jury of eight women and seven men convicted the 16-year-old almost exactly 24 hours after beginning their deliberations.
Jodi, 14, went missing after going to meet her boyfriend in June 2003. Hours later her mutilated body was found close to her Midlothian home.
Jodi's boyfriend Mitchell had denied murdering the 14-year-old schoolgirl in woods near her home in Dalkeith, Midlothian, on June 30 2003.
The judge, Lord Nimmo Smith, told the 16-year-old today that he would face "detention without limit of time".
Addressing Mitchell, the judge said he had been convicted of "a truly evil murder".
Mitchell was found guilty of murder by a majority verdict.
He was also found guilty of supplying cannabis, also by a majority.
Lord Nimmo Smith deferred sentence on Mitchell for background reports.
He said they were required to help determine the minimum period Mitchell would have to serve before being considered for release.