A new, less complex law on gang-related killings is needed to ensure justice for victims and defendants, MPs say. "Joint enterprise" allows groups of people to be charged with murder, even if only one person delivered the fatal blow. Here are some examples.
In July 2008 schoolboy Shakilus Townsend was stabbed to death by a gang in Thornton Heath, south London.
Shakilus, 16, from Deptford, had been lured to the area by a girl, Samantha Joseph in a so-called "honey trap".
But moments after he got off a bus with her he was attacked by members of the Shine My Nine (SMN) gang.
The leader of the gang, Danny McLean, was jailed for life with a minimum term of 15 years. Five other teenagers were also jailed for life.
In September 2009 Joseph was given a life sentence, with a minimum term of 10 years.
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On 9 August 2010 the body of Gemma Hayter, 27, was found on a deserted railway line in Rugby, Warwickshire.
Detectives discovered Gemma, who had learning difficulties, had been attacked by a gang of people after being accused of stealing a £5 note.
Miss Hayter had been beaten and forced to drink urine during her ordeal.
Daniel Newstead, 20, Joe Boyer, 18, and Chantelle Booth, 22, were jailed for life last year. Two other teenagers were jailed for manslaughter.
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One night in August 2007 Garry Newlove, 47, confronted a gang of vandals outside his home in Warrington, Cheshire.
The trial heard he was knocked to the ground and he was kicked "like a football" by some of the youths.
Three teenagers - Adam Swellings, Stephen Sorton and Jordan Cunliffe - were jailed for life for the murder.
Two other youths were found not guilty of Mr Newlove's murder.
Cunliffe's mother Janet claims that although he was present he did not take part and, as he was virtually blind he could not have known what was happening.
Mr Newlove's widow Helen has become a champion of victims' rights and was knighted in 2010.
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In April 2004 Tyrone Clarke, 16, was attacked by a mob of up to 20 youths in Beeston, Leeds.
The gang used makeshift weapons, including baseball bats, poles and planks of wood.
Tyrone was stabbed to death and the following year four men, aged between 17 and 22, were jailed for life for his murder.
The trial heard it was probable none of the four had struck the fatal blow.
His mother, Lorraine Fraser, said she was fiercely opposed to the principle of collective responsibility being diluted.
"I'm sorry someone's responsible, you are in a group, you go out there, and you take someone's life - you're all going down for murder," she told the BBC.
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In the early hours of 19 May 2007 Kevin Johnson, 22, tried to remonstrate with some youths in Sunderland about their rowdy behaviour.
They turned on him and he was stabbed to death.
Dean Curtis, 19, Tony Hawkes, 17, and Jordan Towers, 16, were jailed for life later that year.
Curtis had bragged to friends about having stabbed Mr Johnson.
Towers' sister Ashleigh told the BBC: "Everybody should be held for their own actions only, not somebody else's actions."
But Mr Johnson's father John said: "They acted as a group, they were all carrying knives - they knew what they were doing."
Full story: Stab-death youths jailed for life
In November 2009 Geeta Aulakh, 28, was attacked with a machete as she went to pick up her son from a childminder in Greenford, west London.
Detectives deduced that her estranged husband, Sunny, had hired a hitman to kill her because she had dared to demand a divorce.
The trial heard Mrs Aulakh's hand was almost severed in the attack.
Although Aulakh had gone to a pub to give himself an alibi, he was convicted of murder and jailed for life.
Sher Singh, 19, the alleged killer, and middle man Jaswant Dhillon, 30, were also convicted of murder.
The jury could not a reach a verdict on the getaway driver Harpreet Singh, 21, but he was later convicted of murder at a retrial.
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