A 17-year-old boy has been found guilty of murdering teenager Fico Dougan in a frenzied and unprovoked knife attack.
Uriah Gardner, of Mitcham, stabbed Fico, 17, through the heart with a kitchen knife at the killer's sister's house in Ockley Road, Broad Green, on September 25.
Popular Ruskin College student Fico, of Thornton Heath, died in hospital later that day.
During a week-long trial at the Old Bailey, Gardner's half-sister Tellis Miller, 18, and her friend Montana Riley, now 19, told the court he said rap music made him "want to stab somebody" as he listened to music through headphones on the afternoon of the killing.
Fico arrived soon after to see his girlfriend Miss Riley. Within minutes, 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 in front of Miss Miller's two-year-old sister.
He then fled to his house in Church Path, Mitcham, where police found him burning clothes in his garden.
Gardner's defence barrister David Nathan argued for a lesser conviction of manslaughter on the grounds of diminished responsibility, suggesting the killing had been triggered by post-traumatic stress disorder following the sudden death of his "father figure" brother Leon.
The court heard Gardner, who turned 17 today, saw flies swarming at the window of Leon's house as he discovered the 28-year-old lying dead after an epileptic seizure two weeks before Fico's stabbing.
Dr Tim Rogers, an expert in adolescent forensic psychiatry called as a witness for the defence, told the court the teenager's flashbacks to the gruesome discovery were one of several signs of post-traumatic stress significant enough to impair his self-control.
But a second psychiatrist, Dr Phillip Joseph, called by prosecutor Martin Hicks, said he did not believe Gardner's brother's death was "sufficiently catastrophic" to trigger the disorder.
The jury retired to consider its verdict on Tuesday morning and found Gardner guilty of murder after four hours of deliberation. He will be sentenced on June 24.
Speaking after the verdict, Fico's mother Sandra Opoku said: "Trying to deal with the shock of losing our wonderful, beautiful son has been heartbreaking and very, very distressful for all of us. We struggled to find the words to express the pain and sorrow.
"The initial shock of it all has now given way to the reality that Fico has been killed by someone he did not offend and had no chance to defend himself.
"We now wake up each day wondering what he would have been like now and we ask what was it for? Was there a need for it? Will someone learn from the heartache and distress we are enduring?
"We will want to forgive but how can we ever forget? It is far from easy and we will never be able to find adequate words to describe the impact of losing our darling son, grandson, brother and uncle."
Detective Inspector John Finch, of the Metropolitan Police's Homicide and Major Crime Command, said: "Fico was a talented young man with a bright future a head of him. He was from a close family who have understandably been left completely devastated by his death.
"Gardner’s attack on him was unprovoked and he stood no chance of defending himself.
He added: "I am pleased that the jury have convicted Gardner of murder today. His actions following the murder were calculated and he disposed of the weapon and set about trying to destroy evidence.
"I would like to thank Fico’s family and friends, who have all acted with great strength and dignity throughout what has undoubtedly been an extremely difficult time.
"Whilst today’s conviction will in no way alleviate their grief, I hope it goes some small way towards bringing them some comfort."