A TEENAGER who chased and stabbed a 14-year-old to death in broad daylight over a dirty look was locked up for life today (Friday).

A TEENAGER who chased and stabbed a 14-year-old to death in broad daylight over a "dirty look" was locked up for life today (Friday).

Talented student Martin Dinnegan bled to death in his brother's arms after being knifed in the back by 16-year-old Joseph Chin.

The killer can be named for the first time after a court order was lifted which had previously prevented his name from being published.

Martin had tried desperately to run from his attackers and screamed "please help me" at horrified passers-by. But he was eventually cornered in the street and knifed four times.

An hour earlier Chin's group had spotted Martin and his friends on a bus in north London and they traded aggressive stares.

Chin, of Quill Street, Finsbury Park, was jailed for life and ordered to serve a minimum of 12 years behind bars. He had been unanimously convicted of murder by a jury last month.

After a number of increasingly violent clashes between the two groups in a nearby park, Martin tried to escape the attackers.

Prosecutor Aftab Jafferjee said Martin's death illustrated the "growing scourge of urban posturing" among the youths of Britain.

"It was the equivalent of being hunted in a pack," he said. "Dirty looks turned to death in an hour."

Martin's parents Lorraine and James, who have called on Gordon Brown to tackle Britain's rampant knife culture, were in court today with eldest son James, 20, to see Chin jailed

His friend Kevron Williams, 17, of Bennett Court, Axminster Road, Holloway, was convicted of attempting to cause grievous bodily harm with intent and was detained for four years today.

He was the first to catch Martin on his bike and pulled him to the ground before attacking him with a screwdriver.

The Common Serjeant of London, Judge Brian Barker QC said: "There is no possible excuse or justification, this was really arrogant group violence and the result is totally unacceptable.

"The attack was carried out without any regard for the standards and rules we live by with no though for the victim, his family or his friends.

"The public have every right to be concerned by the increase and growth of this sort of violence.

"It's a tragedy that such triviality caused a young man to lose his life and cause endearing heartache for his friends and relatives."

He added: "This was a deliberate attack requiring a long chase with revenge in mind."

Martin, a pupil at St Aloysius College in Highgate, was the fifteenth teenager to be murdered in London in 2007.

The keen boxer and Celtic FC fan dreamt of studying engineering and was on the eve of starting his GCSEs.

He had moved to London with parents James, 43, and Lorraine, 40, from his mother's hometown of Glasgow 11 years ago.

Martin was heading to a park on a bus in Holloway to meet with some girlfriends on June 26 last year, when glares were exchanged with a group of friends cycling on the same street.

The boys followed the bus and when Martin got off, they clashed for the first time.

As Martin and his friends headed for the park they were pursued again by the youths and within a few minutes the two groups clashed, both bolstered by growing numbers.

Mr Jafferjee told the court: "This case graphically illustrates what the prosecution say is the growing scourge of urban posturing.

"This involves aimless meandering by groups of people who if not actively seeking confrontation are prepared to exploit any pretext in order to engage in aggressive and violent behaviour. The former tends to lead to the latter.

"Such posturing in our towns and cities, while certainly not entirely new, has never the less taken on an even more disturbing dimension in that the ages of those engaging in such conduct an on the receiving end of it are becoming increasingly young.

"The essential part of such posturing is the importance in the minds of these teenagers who are not just prepared to use a weapon but be seen to do so by their peers.

"With such a mindset permeating the streets rapidly escalating spirals of violence are all but inevitable. This is such a case, where dirty looks turned to death in an hour."

CCTV pictures showed the teenager sprinting down Axminster Road, just a few streets from Arsenal's Emirates Stadium, at about 8.40pm, with a group of teenagers, including Chin, not far behind.

Witnesses described how after about 200 yards Martin was surrounded by a gang of youths, before being kicked and punched.

He fell "like a boxer against the ropes" before turning "ashen faced" and collapsing in the street.

Passer-by Thomas Morgan told the court: "I saw what seemed to be a stabbing motion, rather than a punching motion. It was four or five in very quick succession. It seemed to be somewhere from the upper thigh to the lower back."

Another witness, Jeremy Wright said: "Martin had his back to this person. He didn't know he was coming. I thought he was punching him in the back, quite wildly and very, very quickly."

Martin's brothers James and Anthony found him bleeding in Tollington Way, Islington, after getting a frantic call from one of his friends.

Emergency services were called to the scene, but little could be done for the teenager and he was pronounced dead shortly afterwards.

Martin is survived by brothers James, 21, Anthony, 19, and Gerald, 12, parents James, a stonemason, and Lorraine, a nutritionist, and younger sisters Lorraine, 12, and Leanna, seven.

Mrs Dinnegan, in a statement read in court by son James, said: "His bright personality, funny nature and wonderful smile brought much happiness and laughter which we will miss each passing day. Martin was a charming, lovely boy who had left us with cherished memories that will remain with us forever."

Sean Clark, 19, of Bennett Court, Axminster Road, Holloway, and Rene John-Baptiste, 21, of Plaistow, east London, were cleared of all charges after a two-month trial. They were both in the packed public gallery to see their friends sentenced.

Chin was convicted of murder. Williams was convicted of attempting to cause grievous bodily harm with intent but was also cleared of murder.