The Devlin family had put their faith in the criminal justice system to catch and bring the killers of their son Thomas (15) to justice.

But they had not forseen the obstacles that would be put in their way by a service that they believed would be there to help them in their quest for justice.

While police and family knew north Belfast men Nigel Brown and Gary Taylor were the killers, the Public Prosecution Service decided in July 2008, three years after the murder, that there was not sufficient evidence for a reasonable prospect of conviction.

The Devlins say that if they had not battled to overturn that PPS decision Thomas’s killers would still be walking the streets.

In January 2007 they wrote to PPS Director Sir Alasdair Fraser stating they had little confidence in its approach to the case.

In October 2007 the PPS decided that the evidence available was only sufficient to prosecute Brown for attempting to cause GBH to Thomas’ friend Jonathan McKee.

Three months later the PPS received the police files on Thomas’ murder. In July 2008, after examining the files, PPS officials decided there was insufficient evidence to provide a reasonable prospect of conviction.

The family examined similar cases in England and Wales, including that of Nathan Bonnick charged in 2006 with joint venture murder after he handed over his knife to Lloyd Horner who then stabbed Imran Ilyas to death in Sheffield. Bonnick claimed he did not know Horner was going to use the knife to attack Mr Ilyas.

On examining cases such as this the family believed the Crown Prosecution Service would take a different approach to the case against Taylor and Brown and requested a review of the PPS decision by an independent lawyer from outside Northern Ireland.

In August 2008 the PPS informed the family an internal review would be carried out by a senior officer, but not by an independent external lawyer.

The family continued to pressurise the PPS for an external review, which it eventually agreed to. The external review held that the files had compelling circumstantial evidence. The PPS agreed to prosecute and this week a jury found Brown and Taylor guilty.

After four-and-a-half years, the family got justice. But questions are now being asked if the additional grief, stress and anxiety could have been avoided.