Colleagues were not complicit in the murder of an RUC man who was shot at an ice cream parlour in October 1988, the Police Ombudsman has said.
Constable John Larmour was killed by the IRA at the shop on Belfast’s Lisburn Road and no-one has ever been prosecuted.
Members of the officer's family made allegations implicating Special Branch officers and police informants in the killing.
They drew links with a series of other murders and terrorist incidents over a 17-year period.
Investigators interviewed more than 40 witnesses, including retired police officers, considered case papers and forensic files and examined intelligence held by police.
They established that one of the weapons used to kill Constable Larmour was likely to have been originally owned by the RUC.
Ombudsman Dr Michael Maguire said PSNI records did not show to whom it was issued and were unable to establish if it was ever lost or stolen.
"We found no evidence to suggest that Special Branch, or any other element within the RUC, aided, abetted, counselled or procured John Larmour's murder, nor that they could have prevented it,” said Dr Maguire.
"Similarly, we found no evidence to support allegations that police failed to charge suspects in the murder or that they protected IRA members from being brought to justice."