Boy, 12, is cleared of murder after fatal knifing Â

One of the youngest children to be tried at the Old Bailey for murder was cleared yesterday but his older cousin was found guilty of stabbing a 15-year-old to death in a playground squabble.

The slightly built 12-year-old was found not guilty of the "ruthless" crime before leaving hand-in-hand with a court security officer. The older boy was warned he faced a "significant loss of liberty" and remanded to secure accommodation until his sentencing next month. His QC, Edward Rees, said: "There are no winners in this case. One boy lost his life and another boy never had one."

Kayser Osman, whose family had sought sanctuary in Britain after fleeing civil war in Mogadishu, Somalia bled to death on a council estate in north-west London after being knifed in the heart.

His death came after what detectives described as a "classic teenage fall-out over something pretty mundane". Detective Constable Mark Leach, of Metropolitan Police's Serious Crime Group, said: "The incident had started over something as basic as football in the playground and ended with somebody being stabbed with a kitchen knife."

The two boys, who cannot be named for legal reasons, denied murder and the jury acquitted both of the charge but found the older defendant guilty of manslaughter.

Kayser's father, Abdul Kadir Osman, 50, a writer, wept as his solicitor, Louise Christian, read out a statement he had written with his wife ,Marian Abdullah. It said: "Our son Kayser was a peace-loving child who was not involved in any criminal activity. Unfortunately his hopes, dreams and bright future were destroyed."

Calling for a public inquiry, Ms Christian said: "They believed this country would afford a safe haven, but instead of finding security and peace here they have seen their son brutally murdered. Not enough has been done by the Government or police to protect children in places similar to where they were living."

The trial was told a scuffle broke out between Kayser and the 15-year-old near the Acorn Youth Club on Church End estate in Harlesden on 12 March.

As the boys were parted by an adult, the Somalian was heard to shout "I'll remember you" to which the older defendant was alleged to have replied "I'm going to get the biggest knife I can find."

The prosecution alleged that the younger boy was a "ready, willing and knowing assistant" after being ordered by his cousin, then aged 14, to get "the biggest, sharpest knife". He ran home and grabbed a kitchen knife before passing it to the older boy and going to a friend's house.

The 12-year-old insisted he believed the weapon was just meant to scare Kayser.

But his cousin stabbed Kayser – the middle child of five – who bled to death despite "valiant attempts" by a passer-by to save him.

The stabbing was, a "final, ruthless and intentional act of violence" by a boy who was "cocky and boastful" as he walked away from the scene carrying the knife, said Brian Altman, for the prosecution.

The 15-year-old, said to be of a low intellect, insisted he was terrified of the 6ft Somalian boy whom he accused of being a bully "who was for ever picking on me". The boy added: "I was angry. I lost control."

During the three-week trial in which the judge and barristers dispensed with wigs and gowns to make the process less daunting, the defendants were allowed to sit near their legal representatives rather than in the dock.

Abandoned by his parents as a child and sent to live with relatives, the older defendant had been living rough in the months before the stabbing, having run away from foster parents.

Police said the boy showed no obvious remorse over the killing, but Det Con Leach added: "Although he went with a knife and stabbed him I don't think he ever thought further than that. I don't think he ever thought of the death of another person until afterwards."