A teenage girl has admitted filming the death of a Keighley man who was killed by her friends in a so-called "happy slapping" attack.

Gavin Waterhouse, 29, died from a ruptured spleen following the "unprovoked and cowardly" attack in the Beckside area of the town last year.

In what has been hailed as a landmark decision by the Crown Prosecution Service (CPS), a 15-year-old was charged with aiding and abetting manslaughter for using her phone to video the attack on Mr Waterhouse.

The girl, who cannot be named for legal reasons, stood by while Mark Masters, now 19, of Parkwood Rise, Keighley, and a 17-year-old boy beat their victim after stopping him in the street between Morrisons supermarket and Bridge Street.

She admitted the charge of aiding and abetting manslaughter at a hearing at Leeds Crown Court yesterday.

Masters and the 17-year-old, who also cannot be named, have both pleaded guilty to the manslaughter of Mr Waterhouse, who was found dead at a flat in North Street on September 26, 2007.

Following yesterday's hearing, the Crown Prosecution Service said barrister Judith Naylor, who was junior counsel in the case, had made history by deciding to prosecute the teenage girl.

A spokesman for the CPS said: "Two male defendants aged 19 and 17 who attacked Gavin Waterhouse in the Keighley area on the September 23, 2007, have pleaded guilty to the unlawful act of manslaughter.

"Yesterday at Leeds Crown Court, a third defendant, a girl aged 15, has entered a guilty plea to aiding and abetting that manslaughter.

"Judith Naylor made a landmark decision when she advised the female defendant be charged in respect of her actions, namely for recording the attack which led to the death of Gavin Waterhouse on a mobile phone."

Masters and the 17-year-old youth had originally faced charges of murder but then pleaded guilty to a lesser charge of manslaughter. They will be sentenced along with the 15-year-old girl at a later date.

Detective Superintendent Paul Kennedy from the police homicide and major inquiry team, led the investigation. He said: "We are pleased with the outcome of this police investigation following what was an unprovoked and cowardly attack. Our thoughts are with Gavin's family."