A catastrophic failure by prosecutors prevented a jury in the Kiyan Prince murder trial hearing key evidence that the young footballer?s killer had allegedly threatened to stab a girl, according to a judge.

The killer was named yesterday as Hannad Hasan, 17, a Somalian refugee who had been in the year above Kiyan at the London Academy in Edgware, north-west London.

Hasan stabbed him through the heart at the school gates. He was found guilty of murder yesterday at the end of his third trial over the killing.

According to sources, Hasan was obsessed with Somalian gang culture in the UK and was trying to impress members of the notorious Thug Fam, who killed Pc Sharon Beshenivsky.

Kiyan?s parents, Mark Prince, the former boxer, and Tracy Cumberbatch, had to sit through three trials. The jury could not agree on the first, and the second was abandoned after Mr Prince approached a woman juror.

Hasan, who lived with his mother in Colindale, north London, denied murder but admitted manslaughter.

Kiyan, who played for the Queens Park Rangers youth team, was stabbed after he intervened in what was described as a playfight between Hasan, then 16, and a friend in May last year.

Hasan turned on him, got him in a headlock and produced a penknife. The teenager had been in trouble for assaulting pupils and was suspended six days earlier after urinating in front of a teacher and threatening her.

Less the two weeks before the stabbing, he had allegedly threatened to ?shank?, or stab, a girl during a trivial dispute over a bus seat. The allegation was never subject to criminal charges, but witnesses came forward after they learnt of the killing.

But the jury, who had to decide whether Kiyan?s stabbing was an accident or if the youth intended to cause serious injury, never heard of his previous violent outbursts.

However, because the prosecution failed to give the defence sufficient notice, the evidence of the alleged bus incident was excluded.

Mr Justice Wilkie censored prosecutors for only providing the defence with details of the allegation on the eve of the first trial in October last year. He agreed that it would have been ?grotesquely unfair? to expect the defence to deal with the late evidence.

He said: ?The fault lies four-square with the prosecution for failing catastrophically to process this evidence within the time frame to present it as part of a fair trial.?

The Crown Prosecution Service and the Metropolitan Police have begun a review to identify any shortcomings. Legal procedures also precluded his full school record being presented to the jury.

Outside court yesterday, Kiyan?s mother said: ?It was the right verdict. It?s been a horrible journey. I am glad it?s all over.?

The family called for tougher sentences on youths caught with knives to prevent the increasing number of murders among young people. The judge, who had removed an order banning identification of Hasan, adjourned the case for sentencing on July 27.