Boy X: the witness who betrayed his friends for a new identity

Pressured by his family, it was the evidence of a terrified gang member that secured justice

(PA)

At the heart of the August 2007 murder of 11-year-old Rhys Jones was a simmering gang feud fought between underachieving boys and dysfunctional young men from neighbouring council estates. But far from being a sophisticated turf war among well-armed and cash-rich gangsters, the forces that gathered across the Fir Tree Pub car park that fateful night were no more than feckless youths whose dreams of wealth extended little further than a new pair of trainers or a stolen bicycle.

While Norris Green and Croxteth once provided sought-after homes for those seeking refuge from city centre slums, in recent years locals have had to contend with escalating conflict between rival collections of just a few dozen youngsters claiming to represent their communities.

Violence between Norris Green's "Nogga Dogz" (or Strand Gang) and the neighbouring "Crocky Crew" of Croxteth exploded on New Year's Day 2004 with the murder of Croxteth's Danny McDonald, 20, who was gunned down in a packed local pub in front of stunned drinkers. His death sparked a bitter feud and 70 further shootings. Revenge was exacted 20 months later with the assassination of Strand Gang "leader" Liam "Smigger" Smith – widely suspected of killing McDonald. As he stepped out of Altcourse Prison in Fazakerley, he was caught by a dozen Crocky Crew and blasted in the head with a shotgun from five yards.

Police have incarcerated 43 people in connection with the violence but detectives are reluctant to glorify the individuals as dynamic "gang members". Both McDonald and Smith were honoured as fallen soldiers with lavish funerals, but to police they and their followers were "sad no-marks" living on the meagre proceeds of petty crime.

According to Detective Superintendent Dave Kelly, who led the investigation into Rhys's murder, there is little discernible structure to the rival groups. Police reject claims that Rhys's killer, Sean Mercer, held a formal position within the Croxteth Crew or that he had anything other than a "trivial" reason to open fire that day. Previous shootings had been sparked by little more than a stolen bicycle or a misplaced word to a local girl.

"We are not talking about the mafia here, we are talking about kids, teenagers, who lived on a housing estate," explained Det Supt Kelly. Chief Superintendent Steve Watson, responsible for the policing of Liverpool North, said there was little to the gangs. "I do not want to overstate the sophistication of these groups. In essence they are very often a collection of dysfunctional and feckless youngsters who associate purely on the geographical basis of where they live."

Mercer and his friends led unremarkable lives. They spent most days in a cannabis fog playing video games, going to each other's houses and riding their bikes. With the exception of Gary Kays' leased Audi Q7 they shared none of the trimmings of wealth as enjoyed by Merseyside gangster Curtis Warren, who was a hero to many. Most were too young to socialise in pubs or clubs. Few had girlfriends and Mercer's most valuable possession was a £400 bike. When it came to criminal knowledge the youths knew little more than could be gleaned from CSI or the internet, where they placed grainy videos glorifying their criminal exploits. Police said forensic residue could have been removed from Mercer's body just as easily with water as with the petrol the defendants actually used – and which itself provided another useful clue in their hunt.

At the time of Rhys's murder Merseyside Police were engaged in Operation Matrix, a long campaign designed to smash the groupings using every "legal and ethical" option open to them. By August 2007, detectives believed they had half the known members in jail or awaiting trial. Even after Rhys's death the challenge to the gangs continues, with some 5,800 stop-and-searches in the last 12 months. Violent crime is down by more than a fifth, detectives claim.

But fear remains. The reaction in Liverpool to Rhys's murder was one of horror, and Sean Mercer's name was one of the first to emerge, anonymously posted on the internet and sprayed in graffiti across the city. So frightened was Mercer of reprisals that he took to travelling around in the boot of a car.

Yet no one in Croxteth was prepared to stand up with real evidence. Merseyside Police spent five days searching the scene, drafting in 40 detectives to work alongside 200 uniformed officers, but a blanket fear of recriminations stifled the investigation. Although the inquiry appeared to be moving at a snail's pace, detectives needed to build what proved to be a compelling circumstantial case against him. The net was slowly drawing in. Uppermost in the daily police briefings was the need to keep Mercer and his associates alive – they wanted them in court.

The first wave of arrests came three days after the killing, on Saturday 25 August. But there was not enough evidence to charge. So the police installed listening devices, including one at the home of James Yates and another at Boy M's, where details of the murder and the cover-up were discussed. These conversations led police to the nearby home of a 17-year-old, who was later referred to at the trial as Boy X.

On 20 September 2007, one month after Rhys's murder, officers raided Boy X's house and discovered a small cache of guns, including the 1915 Smith & Wesson murder weapon, hidden in the loft. At the time Boy X was on holiday in Florida with his family. Mercer called or texted him 13 times in 15 minutes to warn him of the raid. A terrified Boy X – urged by his stunned family to cooperate – was arrested on the apron at Manchester airport when he returned a week later.

What he told police would make him the star witness in the prosecution case: he described the events of 22 August 2007 and the hiding of the gun. Boy X told how he was called by Mercer 20 minutes after the shooting, who asked him to get in a taxi and pick him up at the home of the teenager responsible for the cover-up, Boy M. Boy X said he took the weapon back to his house where he hid it in the dog kennel, before it was later moved to his loft by Dean Kelly.

The Director of Public Prosecutions decided that Boy X's evidence was so valuable that he should be offered immunity from prosecution, an identity change and a move away from Croxteth in return for his testimony. It is only the second time that police have used their powers under the Serious Organised Crime Act 2005, and the first for a youth. At the trial the defence sought unsuccessfully to discredit Boy X's evidence, claiming he was an experienced gang quartermaster willing to change his version of events to keep himself out of jail.

The intercept evidence had discredited Mercer's alibi, but now detectives were required to build a motive – which meant proving the gunman and his associates were gang members. They did this by compiling a 3,000-page dossier of bad character evidence. Far from hitting a wall of silence, detectives were inundated with leads and in the end 190 witnesses came forward. The problem was finding proof.

Also in Boy X's account was his description of the Hardrock Mountain bike, Mercer was riding on the night of the killing. An insurance claim revealed its serial number matched that of a bike found near Melvin Coy's industrial workshop in the days after Rhys's death.

DNA evidence recovered from the bike helped seal the case against Mercer, along with detailed telephone logs and CCTV footage capturing his movements that evening – culminating in the chilling image caught on camera of Rhys being struck by Mercer's second bullet and falling to the ground, where he died in his mother's arms.