As four people are sentenced for the killing of David Morley in an attack which one of them claimed was filmed on a mobile phone, the BBC News website looks at the issues surrounding "happy slapping".
By Chris Summers
Chelsea O'Mahoney (right) was jailed for eight years
When the first mobile phone camera was launched in November 2000 its inventor probably never imagined it would be used to film people being beaten and bullied, let alone killed.
But sadly that is exactly what seems to have happened in the last few years.
David Morley, a 38-year-old barman, was beaten to death on 30 October last year by a gang of four young people. One of his killers told the Old Bailey the attack had been filmed on a mobile phone.
Jailing each member of the gang for between eight and 12 years, Judge Barker told them: "It seems that three of you had been on
previous expeditions, and had become obsessed with the activity of catching people unawares, assaulting them and filming it for your later gratification.
"You called this 'happy slapping'. No victim on the receiving
end would dignify it with such a deceptive description."
By the time the four were arrested, any incriminating footage had apparently been deleted.
Unlike computers, where hard drives usually retain deleted images, mobile phones are fairly basic devices, and criminals can usually cover their backs simply by getting rid of stills or video footage which might be used against them by the police.
Police believe that if offenders knew they could be caught even if they deleted the images it might put an end to the craze.
One British company is working on ways of recovering deleted images but at the moment it is not a simple process.
One way offenders could be caught is if they send pictures or footage to a friend's mobile phone.
David Morley was picked on at random
But even then the data is only stored on the phone network's server for a short period of time before being deleted automatically, so the police need to act quickly if they are to obtain the crucial evidence.
If a crime is committed, and police discover the identity of the suspects and their mobile phone details quickly, they can intercept this data before it is deleted.
"Happy slapping" is thought to have originated in south London about a year ago but quickly spread across the country.
Largely it was a playground prank in which an unwitting victim was surprised and slapped lightly around the face while his or her reaction was filmed.
But on too many occasions it turned into real violence with gangs bullying children and young adults, or complete strangers being assaulted as part of a mugging.
In the case of Mr Morley his attackers went out on several occasions in the middle of the night and preyed on smaller groups who happened to be out and about.
Reece Sargeant, 21, Darren Case, 18, and David Blenman, 17, all from Kennington, south London, were each sentenced to 12 years in prison for manslaughter. Chelsea O'Mahoney, 16, also from Kennington, was jailed for eight years for the same offence.
Blenman told the jury how O'Mahoney, who was 14 at the time of the attack, approached Mr Morley and his friend and said: "We're filming a documentary about 'happy slapping'."
Mr Morley was then punched and kicked to death.
Dr Graham Barnfield, a journalism lecturer at the University of East London and an expert on the phenomenon, said he believed some "happy slapping" footage echoed the antics of people on TV shows, such as Jackass and Dirty Sanchez.
But he told the BBC News website: "It is all very well when it is staged scenes of consenting adults doing it for their own entertainment, but that is often not the case."
He said there was an unhealthy level of "voyeurism and a lack of self-restraint" among many people who had mobile phone cameras.
Dr Barnfield said this ranged from men filming up the skirts of girls walking down the street, to a Glasgow man who was recently jailed for showing a colleague graphic footage of a beheading in Iraq.
But he said he did not agree that there was a need for new legislation to cope with changes in technology.
"I would argue the opposite. It would be wise to use the existing law to try a few test cases and clarify the law before we go looking for new legislation," said Dr Barnfield.
He pointed out that a judge or magistrate was already entitled to consider the use of a mobile phone camera in an assault as an "aggravating factor" which could lead to a longer jail sentence.
Some people have suggested introducing a new law by which the person holding the camera could be prosecuted even if they did not land a punch or a kick.
Programmes like Dirty Sanchez have been blamed for encouraging happy slapping
Dr Barnfield is not in favour of this idea and added: "There is no need for a moral panic about this. Let's not treat it as an epidemic but use the laws on the current statute book."
Asked about happy slapping, a Home Office spokeswoman said: "The government deplores this practice but we think existing legislation can be used to cover it."
She said a person taking photos could be seen as aiding and abetting an assault and could be prosecuted with the maximum penalty ranging from six months for common assault to life for wounding.
Mobile phone companies are aware of the bad PR and are working to combat the "happy slapping" phenomenon.
A spokesman for Orange said: "We are aware of assaults on members of the public which are captured on video phones. If people are aware of this sort of thing happening they should contact the police."
Sargeant (L) and Case were each jailed for 12 years
He added: "We do visit schools to talk about mobile phone etiquette, including mobile phone bullying."
Broadcasting regulator Ofcom said mobile phone content was outside its remit.
An MTV spokeswoman said shows such as Dirty Sanchez and Jackass were accompanied by "clear visual and verbal warnings informing viewers that the stunts are carried out under the supervision of health and safety professionals, and that no attempt should be made to recreate or re-enact them".
She added: "We also insist that viewers do not send in any home footage of themselves or others performing stunts or other dangerous activities."