THEY came from decent families.

But something turned a group of teenagers into killers in Golcar.

The thugs who attacked and murdered taxi driver Mohammad Parvaiz in what a judge said was a racially-motivated attack that was "savage beyond belief" have been likened to vicious, feral gangs elsewhere in the UK.

But senior police officers and criminal experts disagree.

They believe there was no gang culture involved when the youths lured Birkby father-of-three Mr Parvaiz into an ambush at Field Head, Golcar, on a July evening last summer.

Criminology expert Prof Alex Hirschfield, of Huddersfield University, said: "There have been several incidents of what has been termed 'raging', when people have been viciously attacked by a group.

"There is nothing pathological about any of the individuals involved. But there is a process of escalation in violence that takes place when those people decide to act in a certain way.

"In the case of the Golcar murder, which was really tragic, there was a degree of premeditation. But my feeling is that there was no intent to deliberately kill.

"The violence escalated and led to a loss of control.

"They get a thrill or a buzz out of this type of behaviour and the belief they can escape."

Prof Hirschfield spoke out after four of the youths were handed life sentences.

Christopher Murphy, 18, must serve at least 25 years while Michael Hand, 19, must serve 21 years before he is eligible for parole.

Two younger killers, Graeme Slavin, 18, and Steven Utley, 17, were ordered to be locked up for at least 17 years.

Michael Beeby, 16, and Jason Harris, 17, were detained for 10 and eight months respectively for violent disorder.

The case has been likened to incidents in London, where gangs of youths have hit the headlines in recent weeks.

There have been fatal shootings in south London when rival gangs clashed.

And another gang were jailed for a series of Tube robberies in London which eventually ended in murder.

But Chief Supt Barry South, Kirklees' top police officer, believes the Golcar youths were not part of a gang culture.

He said: "I feel they were a group of individuals who got involved in something which had terrible, tragic consequences.

"I acknowledge there is work to be done in Kirklees to deal with a gang culture, but sometimes we see a group mixing together and anti- social behaviour becomes criminal behaviour.

"These defendants were given long sentences because the judge recognised that this murder was racially motivated."

Kris Christmann, a research associate in Huddersfield University's criminology department, said young people who drifted away from families and parents could become drawn into problem areas.

He said: "There is an issue into how much influence parents are able to exert over the young.

"If there is little or no supervision then peer pressure tells."

Throughout the long trial the court heard how the youths hung around in a Golcar flat used by Slavin and Utley.

They smoked cannabis and drank heavily and cruised the streets of the Golcar council estate in hooded tops.

But their behaviour, while considered anti-social, was never criminal.

Until, that is, they clashed with a group of Asian youths who had been dropped off in Golcar in a taxi driven by Mr Parvaiz.

The group wanted revenge and they got it last July, ordering a taxi they knew would be driven by the man they sought.