Olukorede Fajinmi, 17, was stabbed to death during a gang fight in Beckton, east London, on February 19, 2010.
The teenager from Ilford suffered a single knife wound to the heart during the confrontation outside the Powerleague leisure centre.
Detectives charged a 16 year-old boy with murder and he went on trial at the Old Bailey on October 20 the same year.
The prosecution case was that the killing was linked to rivalry between the Dagenham Boys or ‘DAG’ gang and the Harts Lane gang from Barking.
Prosecutor Ed Brown told the court: ‘Whether planned or not the events in the minutes leading up to his death were the direct result of two groups of youths coming together, some loosely connected with two opposing gangs.
‘The inevitable reality of this case is that young people were armed that night with knives. Had they not been Olukorede Fajinmi would no doubt be alive today.’
Fajinmi and his friends from the DAG gang had left the leisure centre at around 8.45pm when they spotted around 25 members of the Harts Lane gang, including the 16 year-old boy.
The smaller group of around ten Harts Lane boys gave chase and Fajinmi, otherwise known as ‘Shadow’, grabbed hold of the 16 year-old near a zebra crossing in Jenkins Lane. In the scuffle that followed Fajinmi was stabbed in the heart and the younger boy was stabbed twice in the shoulder.
On November 4, the 16 year-old boy was cleared of murder and manslaughter on the judge’s direction on the basis he acted in self defence.
The Recorder of London, Peter Beaumont QC, said: ‘Starting on the premise that it was [the 16 year-old] who caused the deceased’s death by stabbing in the chest, the Crown has nevertheless to prove that he caused the death unlawfully.
‘That is to say not in necessary and reasonable self defence. In focusing on that issue and examining the evidence available to the prosecution I have come to the conclusion that the prosecution do not cross that threshhold.’
The prosecution dropped a charge against a second teenager who was said to have stabbed the 16 year-old boy in the shoulder in revenge for the killing of Mr Fajinmi.
In August 2011 the DAG and White Hart gangs clashed in Ilford resulting in the death of 17 year-old Kelvin Chibueze, said to be a friend of Olukorede Fajinmi.