A 16-year-old youth has been given a life sentence for stabbing to death a schoolboy who gave him a "dirty look". Lawyers said Martin Dinnegan, 14, was chased and stabbed near his home in Holloway, north London, after exchanging "dirty looks" with a gang. Joseph Chin was found guilty of his murder at the Old Bailey last month. Kevron Williams, 17, was sentenced to four years for attempting to cause grievous bodily harm during the attack in June 2007. Chin was sentenced to life, to serve a minimum term of 12 years. Judge Brian Barker said: "The public have every right to be concerned about the growth of this sort of violence. "It is a tragedy that this sort of triviality caused such a young man to lose his life and has caused enduring heartache to his friends and family." Outside court Martin's mother Lorraine said: "The pain that Martin's death has caused for our family is indescribable. "We as a family will never make sense of the unnecessary suffering that was inflicted upon Martin." She added: "Life will never be the same, a piece of our heart has been taken." 'Vengeful attack' The court heard that the row began when a group on a bus and another group on bikes gave each other "dirty looks". The youths on cycles then followed the group from the bus. The groups clashed twice - first in a nearby park then an hour and a half later next to a housing estate. In the second confrontation, Martin and another youth clashed with Chin, who was left with a cut on his shoulder. Martin then fled, chased by members of the rival group. He fell to the ground and was stabbed four times in the back by Chin. The judge told him: "This was a vengeful attack out of all proportion to what may have gone before and no mercy was shown." He said Williams had led the hunt for Martin out of a "determination to be involved" in the violence. 'Better people' During the trial prosecutor Aftab Jafferjee QC said that teenagers showing off in front of their friends and being prepared to use violence was now a scourge of cities and towns. "This is such a case, which leads from dirty looks to death in one hour," Mr Jafferjee said. Mrs Dinnegan said she was "pleased" with the sentences. "We are just hoping that the people who have been involved with Martin's murder will learn from what has happened to Martin," she added. "We hope they come out of it better people." Source: BBC