Deborah Orr: This is what happens when only a gang makes you feel you belong

What's inside the head of Sean Mercer, the 18-year-old who was yesterday found guilty of the murder of Rhys Jones, 11, on 22 August last year? How he makes sense in his mind of what he has done, can only be guessed at, because Mercer himself refuses to speak. He even declined to give evidence to the court in his own trial.

The indications are that he is remorseless. It has emerged that he already knew that the second bullet from his First World War revolver had hit a "kid", when he fired his third. He was certainly impervious to the pleas of Rhys's parents Stephen and Melanie Jones for the killer of their son to give himself up.

Reports from Liverpool Crown Court say that Mercer gave little reaction to the guilty verdict, beyond going pale and repeatedly puffing out his cheeks. He did, however, hug one of his fellow defendants, and grasp the hands of another two, before he was led away. The young men found guilty yesterday were also said to have laughed shortly after the verdict at a joke one of them had made.

Reports from the court also say that Mercer's father, Joseph McCormick, sat with tears rolling down his cheeks, and mouthed "I love you" at his son. His mother Janette Mercer, was not in court yesterday, but has been present at other times during the 10-week trial. At one point, her son had greeted her with a thumbs-up sign. She has also been charged in connection with the case, alongside three others, of perverting the course of justice.

Little is known of Mercer's family background, except that he lived with his mother and two siblings, without his father, who worked in nightclubs around the city. Mercer left school at the age of 14, "by mutual consent", by which time he had already attracted the attention of the law.

Mercer was a few weeks shy of 17 when he killed Rhys Jones, and his entire adolescence had been conducted under the eye of the police. He was placed under a three-year anti-social behaviour order just days after the murder, following a series of incidents in which Mercer and some friends had terrorised the staff of a sports centre.

Between the ages of 14 and 16 Mercer had been stopped in the street 80 times by the police. He had been convicted of possessing a CS gas canister, and eight months after Rhys's death, he had been given a conditional discharge for possession of cannabis.

Much has been made of his membership of a local street gang, which he had joined in his early teens. He is said to have been "rising through the ranks", although those with some experience of the workings of Liverpool street gangs say that the phrase is misleading. They suggest that there is not much in the way of "rank" in such gangs. Status is afforded to those who inspire the most fear, and fear is generated when people are able to demonstrate their detachment from such regrettable qualities as empathy, guilt or impulse control.

Talk of "ranks" tends to accept gang members at their own assessment, particularly their assessment of themselves as "soldiers". Yet the most challenging thing about these groups is that they are not disciplined. They commit crimes, and deal in drugs. But they are not organised, and that is precisely why they perpetrate such senseless and attention-seeking crimes. They have no real interests to protect and no real assets to guard, not even illegal ones.

Liverpool was identified in 2007 as Britain's centre for organised crime outside London, with 24 prosecutions in the city in the first year of the Serious Organised Crime Agency's operation. This background invites the supposition that the street gangs are in cahoots with organised criminality. John Heale, whose book One Blood charted the rise of "Britain's new street gangs", argues that while organised criminals are aware that members of the youth gangs can be useful to them, the violent crime occurring between disorganised groups of youths tends to be "expressive, rather than instrumental", and among people "who fought others for respect, on a territorial basis and under the name of a gang." This description undoubtedly fits with what is known about Mercer's own motivations. His attachment to Croxteth, and his extreme antipathy to nearby, and similar, Norris Green, is typical of a street-gang mindset. Why it is that street gangs should feel such misplaced loyalty to the deprived neighbourhoods that their actions only further destroy?

All that makes sense is the idea that they form such a fervid attachment precisely because of their lack of a sense of community or belonging. The little they have is all they've got, and their heightened identification with it is bravado, an assertion that if it is theirs then it must be terribly valuable, and therefore well worth jealously guarding.

Likewise, the great emphasis placed on "loyalty" within the gangs – that quality that allowed Mercer to call quickly at least half-a-dozen confederates in covering up his crime – can only be understood in terms that invoke a similar alienation, from family, community and even from institutions that ostensibly exist to nurture young people – such as schools or sports centres. They feel they only have each other, and their actions only strengthen that link.

Psychologists suggest that the fierce loyalty to place and to people that is displayed by young gang members can best be explained as a counter-intuitive expression of their own shame at their own circumstances - the lack of support and dearth of achievement that has been apparent to them since they were very young.

They demand "respect" and take offence at a stray glance in their direction exactly because in the eye of their mind everyone is looking at them, and feeling contempt for what they see. They think little of those they main or kill because every victim is a hateful reminder of their own long-standing sense of powerless victimhood.

Such musings are often dismissed as being perverse – a grotesque focus on the perpetrators of crimes and their shortcomings, when it is the victims of crimes that ought to be society's concern. Yet only by getting to the root of the motivations of those who terrorise and wound can there be any hope of intervening to change the destructive and sometimes murderous course of the perpetrators' lives.

We know a good deal about the parents of Rhys Jones – that they are hard-working and conscientious parents, who cared passionately for their two sons. We also know that in the midst of their mourning, before they had even seen the killer of their son brought to justice, they founded a charity, Liverpool Unites, which aims to raise the cash to build a community centre.

Their gesture speaks of great understanding of the systemic failures that conspired to lead an individual into causing the death of their son. The lives and the hearts of the Joneses are open, for all to see, because they have nothing to be ashamed of. It's a good bet that Sean Mercer, before he stopped feeling at all, may have felt little else but hateful, self-annihilating shame.

d.orr@independent.co.uk