Sentencing him today, Judge John Lodge, QC said: "The events of the 29th of October are tragically typical of the cancer that is gang culture and knife crime."
He said there was "not a shred of evidence" that Joseph or his two friends were armed at the time of the attack or that the defendant was acting in self defence.
"It was a deliberate attack with intent to cause, at the very least, very serious harm."
He described how Boudjellel, 19 at the time of the offence, had come from a "difficult" home life and was the victim of bullying before embracing knife culture.
The judge had earlier directed the jury to find four teenage co-defendants not guilty of murder and causing grievous bodily harm.
A police carrier happened to be driving by at the time of the killing and officers jumped out to chase down Boudjellel and try and save Joseph's life.
Boudjellel was seen to throw the bloodied knife over a wall as he was chased into the Garratt Lane Burial Ground.
Joseph died that afternoon in St George's hospital, despite the best efforts of medical staff.
DNA analysis showed the blood on the knife matched Joseph's blood, jurors heard.
A second 15-year-old boy, who cannot be named, was stabbed in the arm and was taken to hospital after police found him rolling on the floor in agony.
He was treated at St George's hospital for two days before being discharged, jurors heard.
Natalie Marafini, Joseph's mother fought back the tears as she read out an impact statement.
"He wanted to learn to drive, to visit America, to see the world, to make something of his life," she said.
Joseph's brother Samuel leaves the back open every day for him to come home, she continued.
"I have become a shadow of my former self, longing for the day to end but dreading sleep," the mum added.
Addressing Boudjellel directly she said: "When you speak my son's name you disgust me.
"When I look at you in court you refuse to look at me because you and I know the truth.
"What you did that day was pure evil."
Dean George, defending, said Boudjellel was in a particularly vulnerable position because of his mother's mental illness.
He said his client showed a level of remorse when taking the stand during his trial.
"There was an outward, at least, emotional display by him and recognition of the impact," he added.
The court was previously shown CCTV footage of the group walking around Southside Shopping Centre, going into a JD Sports and eating in Five Guys shortly before the attack.
https://www.mirror.co.uk/news/uk-news/🤬🤬🤬🤬-who-murdered-boy-knifing-25486776
