Kevin Nunes was found dead in a country lane in Pattingham in September 2002
Nine police officers, including two chief constables, will face no criminal charges over the investigation into the death of a man who was shot in an "execution-style" killing.
Suspected drug dealer Kevin Nunes, 20, was killed in Staffordshire in 2002.
Five men jailed for murder had their convictions overturned due to concerns over evidence available to the defence.
Fourteen officers in total have now been told by the CPS they will not face charges over the handling of the case.
Among the officers investigated were:
Police believe Mr Nunes, from Wolverhampton, was a drug dealer who was shot after straying into another gang's territory.
Announcing its decision, the Crown Prosecution Service (CPS) said it had investigated a decision to delay a complaint inquiry until after the trial.
It also looked into the failure to disclose a report into the management of a unit that handled sensitive witnesses, including the main trial witness.
The nine officers, four of whom are still in service and five now retired, were investigated either on suspicion of attempting to pervert the course of justice or criminal misconduct in a public office.
The CPS said that when the Court of Appeal overturned the five men's convictions in 2012 it had been concerned about the decision not to investigate the complaint until after the trial, something it said "was wrong".
"We agreed with the Court of Appeal at the hearing and for the avoidance of doubt we still agree," the CPS said, although it added there was not enough evidence to show the decision was a deliberate attempt to pervert the course of justice.
Regarding the second matter, the Court of Appeal called the decision not to disclose the report into the management of the unit "a very bad case of non-disclosure" and the CPS said it agreed.
However, the CPS concluded there was not enough evidence to prove a decision had been taken to conceal the report deliberately.
The Independent Police Complaints Commission has said it will release the details of its findings into the matter soon.