Man guilty of murder, but rape is not proven
A jury took just two-and-a-half hours to find Barker guilty of murdering 17-year-old shop worker Robbie Thomson in Coupar Angus on 26 March last year.
After an 11-day trial, the jury of eight women and seven men at Dundee High Court reached a verdict of not proven in relation to a charge that Barker raped a 19-year-old woman on the same night.
Judge Lady Clark of Calton told Barker that he had been convicted of "a very serious offence".
She said: "I should express the sympathies of the court to the family and friends of the deceased. It was a terrible and horrible death."
Lady Clark also thanked the jury for their "attention, patience and responsibility".
Earlier in the trial, Barker's solicitor advocate Iain Paterson told the court there was "no dispute" that his client was responsible for Thomson's death.
He claimed that he was provoked into stabbing Thomson and that any sexual acts between him and the alleged 19-year-old rape victim were consensual.
Forensic medical examiner Dr Enrico Risso earlier said that Thomson had died from the "combined effects" of 11 stab wounds and drowning.
He added that Thomson "had a number of defensive injuries" from putting his arms up to protect himself and had been stabbed with "substantial force".
The jury had also heard that Barker admitted to prison officials that he had "done a murder" after being arrested for rape.
After the verdict, sentence was deferred until next month for reports.