A "budding psychopath" who knifed to death a popular teenager just six minutes after meeting him has been jailed indefinitely.

Uriah Gardner, 17, of Mitcham, will spend a minimum of 14 years behind bars for the brutal and unprovoked murder of Fico Dougan, in Broad Green on September 25 last year.

Former Archbishop Tenison's High School pupil Fico, 17, of Thornton Heath, had been visiting his girlfriend at the house of Gardner's half-sister on the afternoon of the killing.

Gardner stabbed him repeatedly in front of the two women and a two-year-old girl, with the fatal wound passing through Fico's heart.

He had denied murder on the grounds of diminished responsibility, with his barrister David Nathan suggesting the killing had been triggered by post-traumatic stress disorder following the sudden death of his "father figure" brother, Leon.

But Gardner, who had a history of violent offences including sexual assault, violent disorder and causing grievous bodily harm, was found guilty on May 20.

During a week-long trial at the Old Bailey, Gardner's half-sister Tellis Miller, 18, and Fico's girlfriend Montana Riley, now 19, told the court he said rap music made him "want to stab somebody" as he listened to music through headphones and rocked back and forth in the hours before the murder.

Croydon Guardian:

Uriah Gardner was jailed today

After Fico's arrival, Gardner rose from his seat "with a vague stare" and walked to the kitchen, where he picked up the blade he used to stab Fico at least six times. He then fled to his house where police found him burning clothes in his garden.

Following Gardner's conviction, Judge Stephen Kramer asked for an independent psychiatriac report before sentencing him this morning. The report, by Dr Alexandra Lewis, agreed with prosecution witness Dr Phillip Joseph's assessment that Gardner was a "budding psychopath" but could not yet be diagnosed with any "acute mental illness." 

In mitigation, David Nathan told the judge: "[Gardner] asked me to say to you that whatever sentence you impose that he is deeply sorry for what happened and he does not himself understand why he behaved as he did.

"It is very difficult for me to seek go inside this young man's head and to try and explain to the court what caused him to behave in this appalling way with horrific consequences that it had." 

Judge Kramer told Gardner he had robbed Ruskin College student Fico's family of "a much-loved son, grandson, brother and uncle." He added: "This was rightly described as a senseless killing of someone you had only met and been with for only a few minutes."