The boy, who cannot be named, for legal reasons, admitted stabbing to 53-year-old Christopher Barry in the chest in The Broadway, Edmonton on 14 December last year.
The Old Bailey heard Mr Barry argued with a group of
youths trying to get into a party in his block of flats. He was
followed inside and attacked.
The court heard the boy had been in a gang since the age
of 10.
The boy and his friends had left a 13th birthday party
and had returned later but went to the wrong block of flats, the
court heard.
When they were trying to access the flats they came
across Mr Barry, known as Jack, who refused them entry causing some
"pushing and shoving" between them.
The
boy followed Mr Barry into the lift and pulled a kitchen knife from
his rucksack and said: "What you saying now? What you saying
now?" before stabbing him twice.
The
Old Bailey was told Mr Barry had not realised he had been injured and
returned to his flat where he later collapsed. He was pronounced dead
at the scene by paramedics.
The
prosecution said the boy had previously been warned about handling
knives and described the murder as a "cowardly and unprovoked
attack" over a "trivial dispute".
During
the hearing Mr Barry's girlfriend, Sabrina Finn, who was with him at
the time, said her "heart was broken" following Mr Barry's
death and "life would never be the same again".
In
mitigation, the boy's defence team said he was "full of remorse"
and had pleaded guilty at the earliest opportunity, which Judge
Stephen Kramer said he had taken into consideration.
