While our investigation found that Detective Chief Inspector Tagg should have been more forcible and clear in advising prosecution Counsel of the immunity issue, he did not intend to deceive in his evidence provided at Crown Court. We found no evidence to corroborate the assertion that DCI Tagg knew of or sanctioned the offer of immunity prior to it being given at a public meeting by DI Kiyani.
DCI Tagg may have told Counsel about the immunity issue, but on the basis he should have done so with greater clarity and conviction the IPCC recommended management intervention to remind him of his responsibilities as a senior investigating officer.
The murder investigation was a complex, high profile one and it was vital that it was carried out in a way that could command the confidence of all communities in Birmingham. While we cannot say what impact this issue had on the trial or the verdict, the bereaved families publicly placed their faith in the criminal justice system but they understandably feel that they have been failed by the system they trusted.
The IPCC said there was "no case to answer" for misconduct against the man who led a triple murder investigation arising from the riots in Birmingham in August 2011. Detective Chief Inspector Anthony Tagg was in charge of the criminal investigation.
However, the police watchdog did say the family liaision officer, Detective Inspector Khalid Kiyani, who retired in October 2012, "would have had a case to answer for gross misconduct".
The watchdog said both officers' record-keeping was "deficient".
Haroon Jahan, Shazad Ali and Abdul Musavir were killed when they were hit by a car in Winson Green during the riots in Birmingham.
It emerged during the trial that defence barristers were never told of an offer made by police of immunity from prosecution for witnesses involved in the disorder until the 10th week of court proceedings.
The IPCC said the Crown Prosecution Service had since concluded there was "insufficient evidence to provide a realistic prospect of proving that either police officer had knowingly made a false statement and as a result committed the offence of perjury".
Eight men were acquitted of the murders in July 2012.
The criminal investigation into the deaths of three men in the Birmingham riots was mishandled, according to the independent police watchdog, but it is unlikely any officer will face action over the failings.