A 15-year-old girl who filmed a man being beaten to death in a so-called "happy slapping" attack in West Yorkshire has been detained.
Gavin was beaten "like a punch bag", the court heard
The girl, who cannot be named, will serve her two-year sentence in a young offenders' institution, for her part in the death of Gavin Waterhouse, 29.
She was convicted of aiding and abetting manslaughter in the attack on Mr Waterhouse on 23 September 2007.
A 17-year-old boy and a man, 19, were sentenced for manslaughter last week.
The Crown Prosecution Service (CPS) said the girl's conviction was the first of its kind in the UK.
Sentencing the teenager, Judge James Stewart said: "I've received a most moving letter from your mother about the way you were brought up and the shortcomings of modern society.
"But it is only by making an example of youths like you that the court can do its best to try and change things."
At an earlier hearing, Mark Masters, 19, of Parkwood Rise, Keighley, was ordered to serve seven years in a young offenders' institution for killing Gavin Waterhouse.
Sean Thompson, 17, of Parkside Terrace, Cullingworth in Bradford, was ordered to serve six years for the 29-year-old's death.
Leeds Crown Court heard Mr Waterhouse, who had a drink problem and was in bad health, had been drinking alone behind Morrisons supermarket in Keighley, when the pair attacked him.
The judge said the pair "rejoiced in what they'd done"
The girl first asked Mr Waterhouse for 40p and when he refused Masters told her to film it as he repeatedly punched Mr Waterhouse in the face.
The court heard Thompson then pulled the victim to the ground where the pair took turns to kick him in the body.
The victim died of a ruptured spleen three days later, alone in his flat.
The trio bragged about what they had done and showed the video clip to other people.
But Abbas Lakha QC, defending, said the girl had no idea of the violence about to take place when she was asked to film it.
Speaking after the sentencing, Det Supt Paul Kennedy said the conviction was "new territory" for the police and the CPS.
He added: "The real overriding feature of it throughout the investigation was just the unprovoked, brutal nature of it.
"The further different aspect to it was the filming, the encouragement by the 15-year-old.
"You can't help but feel sick to death of the mindless violence."