Kevin Nunes murder: Chief Constable stopped probe that may have derailed gangland murder case

A legal report prepared for the Court of Appeal states that Mrs Sawyers, then a superintendent in charge of professional standards, took the decision to delay looking into complaints of racial discrimination made against Det Insp Joe Anderson, then head of the Sensitive Policing Unit (SPU), by the force's star witness Simeon Taylor and his mother Patricia Munn.

The document says officers and lawyers – including Mrs Sawyers – were concerned that investigating the grievances, which were later proved to be frivolous and more than likely instigated by disgruntled police officers, would derail the case built against five men for the murder of the 20-year-old footballer in a country lane in Pattingham, South Staffordshire, in 2002.

DI Anderson had angered his colleagues by holding them to account and bringing in new working procedures in the department he joined in 2005 and described as 'dysfunctional'.

Taylor and his mother, accused of 'manipulating' the witness protection scheme and officers 'to their own advantage', made official complaints in January 2006. The murder trial was still one year away but Mrs Sawyers sought the advice of the Crown Prosecution Service (CPS) about whether investigating the complaints should be delayed.

The court document states: "Whilst awaiting clarification Supt Sawyers made the decision that the complaint investigation would remain sub-judice."

It states that on June 27, CPS lawyer Mark Sheppard wrote to prosecuting counsel Christopher Millington QC with details of the complaints.

A note read: "The prosecuting lawyer has recently been visited by officers who have been tasked to deal with the complaint, they are concerned that any investigation into this matter could undermine the evidence of Simeon Taylor thereby making it disclosable to the defence.

"Given the potential that the defence will argue inducement and perhaps seek to examine what arrangements have been made to care for Simeon Taylor, the prosecuting lawyer takes the view that any investigation is sub-judice and consequently no further action should take place until after the conclusion of the trial. Counsel is asked for his opinion on the matter."

The document continues to say that Mr Millington indicated that the most important thing was to 'keep Simeon Taylor on board'.

By December of 2006, Mr Sheppard had told officers that it was inappropriate to continue investigating the complaint, stating: "The effect of continuing the investigation at present could have the potential to impact upon the trial," according to the document.

But the Court of Appeal note came to the conclusion that: "If the reason not to investigate was the fear that something might need to be disclosed that supports the argument that an investigation was required.

"The fear that something disclosable might arise cannot be an excuse for ignoring the complaint. It might be argued that there was a concern about what DI Anderson might say in response hence the decision not to investigate.

"An investigation after a trial might reveal something, which should have been disclosed at trial, hence the need to investigate it as it arose. There was no justifiable reason for taking a course of action that prevented those complaints from being disclosed."

Five men jailed for the murder had their convictions quashed after serious police failings were revealed.

Deputy Chief Constable, Nick Baker, of Staffordshire Police, said: "The Independent Police Complaints Commission (IPCC) has undertaken a long and detailed inquiry into Operation Kalmia, including the actions of witness protection officers and others involved in reviewing their actions.

"Until the report is published, which remains the responsibility of the IPCC, Staffordshire Police cannot comment further on specific questions relating to Kalmia.

"Again, we reiterate that Kalmia was reviewed by the Crown Prosecution Service, which concluded that none of the officers involved should face any criminal charges."