Romello Harley, 19, of Kirkdale, SE26, was convicted at Inner London Crown Court of the murder of Tashawn Watt.
Police were called shortly after 9.30pm on 25 June last year after nineteen-year-old Tashawn was found collapsed in Miall Walk, in Sydenham.
Officers attended along with London Ambulance Service, but despite the best efforts of emergency services, Tashawn died at the scene. He had been stabbed in the chest.
Detectives from the Met’s Specialist Crime Command began a murder investigation and started urgent enquiries to work out why Tashawn had been attacked.
Police said they established that Harley had been involved in an argument with a relative of Tashawn’s at the Watt’s family home a short time before the incident which resulted in Harley being asked to leave.
The court heard how he then went to arm himself with a knife before returning to the area and tried to lure Tashawn to an alleyway, but Tashawn refused to go with him. Harley then stabbed Tashawn in front of his family.
Harley is then said dropped the knife and ran away from the scene. As well as there being several witnesses to the incident, the attack was also caught on CCTV.
The court was told that Harley went into hiding and officers began an urgent manhunt to locate him. But just three days later on 28 June, he handed himself in at Lewisham Police Station and was arrested on suspicion of murder.
Detective Chief Inspector Chris Wood, who led the investigation, said:”My thoughts remain with Tashawn’s family as they continue to come to terms with the loss of their loved one in such awful and needless circumstances.
“I am pleased that as a result of our investigation we have delivered justice for them by ensuring the person responsible for Tashawn’s killing will spend a considerable time behind bars.”
A post-mortem examination carried out after Tashawn’s death found he had died from a stab wound to the chest.
Harley will be sentenced at the same court on a date to be set.