Killer taxi driver Christopher Halliwell faces a whole life sentence when he is jailed later for his second murder.
He is already serving a life-sentence for the murder of 22-year-old Sian O'Callaghan, who he abducted in his taxi as she made her way home from a night out in Swindon in March 2011.
Halliwell confessed to killing Miss O'Callaghan and took police to her body before offering "another one" and leading them to where he had buried missing sex worker Becky Godden several years earlier.
He later denied the murder of Becky Godden - who went missing aged 20 in 2003 - but it took a jury at Bristol Crown Court less than three hours to find him guilty.
As the jury returned their verdict, father-of-three Halliwell smirked at Miss Godden's family.
Judge Sir John Griffith Williams told him he faced either a whole life order or a "significant" minimum term of imprisonment.
The case almost didn't get to court despite Halliwell confessing to police five years ago, saying: "I'm a sick f*****. Normal people don't go around killing each other."
But his admission was ruled inadmissable in court as Detective Superintendent Steve Fulcher breached police guidelines by failing to caution and offer him a solicitor.
The detective resigned from Wiltshire Police in May 2014 after being found guilty of gross misconduct.
Miss Godden's mother Karen Edwards has campaigned for changes to the Police and Criminal Evidence Act (Pace) following the case.
Speaking outside of court, she said she would like to thank Mr Fulcher from the "bottom of my heart" for "bringing my little girl home".