Arsema Dawit was knifed to death by Thomas Nugusse just three days after her 15th birthday in June 2008 at a block of flats in Waterloo.
Her family had reported him to the police around five weeks before she died, saying he had threatened to assault and kill her, but they did not feel their concerns were taken seriously enough by police.
Today an inquest heavily criticised the police for its handling of the case.
Police were criticised today for failing to act fast enough to save the life of a teenager stabbed more than 60 times by her jealous ex-boyfriend.
Arsema Dawit was just 15-years-old when she was killed by Thomas Nugusse at a block of flats in Waterloo in 2008.
Her family reported him to police weeks before she died saying he threatened to kill her.
Today Arsema's mother says she feels "vindicated" after an inquest heavily criticised the police for its handling of the case.
A jury at Southwark Coroner's Court condemned the police investigation into the family's concerns, saying her complaints were not treated with sufficient urgency because they were inadequately recorded.
Arsema's mother Tsehaynesh Medihani said outside court today, "The police did nothing to stop Thomas Nugusse from carrying out his threats to kill Arsema just three days after her 15th birthday.
"I have had an agonising four weeks reliving the nightmare of those last few weeks of my daughter's life.
"While the pain and loss of my daughter will never go away, I can take some comfort from the fact that the public now know the truth that Arsema's death was avoidable and that her life could have been saved if the police had acted."
The unlicensed events unfolded on Saturday night at Clapham Common and Tooting Bec Common.
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