A teenager is beginning a life sentence for the "senseless" murder of a 15-year-old boy who was riding his bike with his friends.
Joshua Williams, 18, from north London, was found guilty of the murder of Alan Cartwright, 15, on Thursday at the Old Bailey and was told on Friday he would spend a minimum of 21 years in prison.
He was also found guilty of conspiracy to rob and given a further eight-year sentence that will run concurrently. The jury took three hours to convict him.
Two other teenagers, Shaquille Roberts, 18, and a 17-year old boy from Haringey who has not been named, have previously pleaded guilty to robbery and are awaiting sentencing.
Cartwright was cycling with five friends near his home on 27 February when they were stopped by two boys who tried to take their bikes.
The court heard that it took seven seconds for the two boys to step out in front of the five cyclists, while a third boy, Williams, swung at Cartwright's chest with a knife in what prosecutor Jonathan Rees QC called a "gratuitous and deliberate" stabbing.
Cartwright managed to cycle on to a local swimming pool but was pronounced dead at the scene.
CCTV footage of the attack was released by police at the time – and it was a comment underneath a YouTube video of the incident that led to Williams' conviction.
View this video on YouTube
A comment that was widely copied and pasted underneath this and other versions of the footage named one of the culprits as Slimzy, Williams' street alter ego.
After being identified, Williams went to a police station with his parents, telling one officer, "It's the right thing to do, isn't it?"
However, he later claimed that he was only there to clear his name and that he was at a youth club at the time of the killing.
But this line of defence fell apart after jurors noticed Williams' family failed to swear on the Bible when giving evidence in court to support what judge Rebecca Poulet QC called a "false account", the Press Association reported.
She pointed out that the severe sentence could have been less if he had pleaded guilty.
The family's lawyer argued that by not swearing on the Bible they were in fact following the Bible's own teaching that "swearing oaths is not acceptable".
The judge told Williams that the attack was motivated by "greed" as she handed down the sentence, the PA reported.
"This was a gratuitous and senseless piece of violence," she said. "It was motivated by acquisitive greed and the incident has rightly horrified and dismayed the public.
"Alan was a wholly innocent boy who was unconnected with gangs. You have taken his life in a pathetic and unsuccessful attempt to steal a bike.
"The whole incident was captured on CCTV. We watched you, Joshua Williams, step out with deliberation and swing your left arm at the upper chest of the first boy in the line of cyclists. The action is very swift but firm and fatal."
Bernard Richmond QC, defending, said: "The point I am asked to make is young people do think in very different ways and make very wrong decisions."
Cartwright's family, who were in court to hear the verdict, have called for police to stop and search more people on the street and for mandatory 10-year sentences for people carrying knives.
