Nina Lakhani: So what went so very wrong in the Sam Hallam case?

When Hallam came to trial in 2005, the case against him had seemed weak. There was neither forensic evidence nor CCTV footage linking him to the attack on Essayas Kassahun and his friend, Louis Colley.

The prosecution had just two material witnesses. The first, Phoebe Henville, told the court she'd seen Sam Hallam among the group that carried out the attack, but changed her story several times to police and in court. She did not know Hallam, but had heard 'rumours' that a 'Sam' was involved. She claimed he was one of the killers after coincidently bumping into him in the street.

The second witness, Bilel Khelfa, told the police that he had seen Hallam standing over Kassahun, wielding a baseball bat with a screw protruding from its end. But he retracted this in court, saying he named Hallam only because Henville told him he was involved.

The prosecution also claimed that Hallam had concocted a false alibi. After his arrest, Hallam told police that he had been playing football with a friend, Timmy Harrington. But Harrington said he hadn't seen Hallam at all that week.

In court, Harrington was much less sure - his memory was poor because he smoked a lot of cannabis. A photo retrieved off Hallam’s phone by Thames Valley Police show they were together a day after the attack.

Hallam’s mobile phone was never interrogated by the Met, to figure out who he had called or when, and which phone mast he was nearest at the time of the attack.

Together with Bullabeck Ringbiong - against whom the evidence was much stronger - Hallam was convicted and sentenced to life.

Thames Valley officer interviewed several new witnesses on behalf of the CCRC who had come forward to say Mr Hallam was not involved.

Their investigation turned up an important new line of inquiry: that the ‘Sam’ mentioned by the witnesses was another Sam, not Mr Hallam, whose identity was ‘called in’ by a local man. This lead was never followed up and the message was never disclosed to Hallam’s lawyers.

The ‘statement of reasons’ by the three CCRC commissioners, explaining their decision to refer the case to the Court of Appeal, included trenchant criticisms of the Met inquiry.

It was a “poor-quality investigation”, while the record-keeping, was “just a disaster”, they said. DCI Mick Broster, the senior investigating officer, was heading 14 other major inquiries at the same time, most of them homicides. “There was simply no control over this investigation,' said one commissioner, “not because of dishonesty, but poor management and staff shortages.”

Since 1997 the CCRC has referred 500 cases to the Court of Appeal. Around two thirds have been upheld, in that convictions have been quashed or sentences reduced. This includes overturning more than 70 murder convictions. If, as expected, Sam Hallam’s conviction is quashed today, he will make him one youngest victims of such a serious miscarriage of justice. The youngster has lost eight years of his precious life, and his father to suicide, meanwhile Essayas Kassahun’s family must be wondering whether his killers will ever be bought to justice.