Events before and after the murder of an RUC officer 27 years ago are to be investigated, Northern Ireland Police Ombudsman Ms Nuala O'Loan confirmed tonight.
Sergeant Joe Campbell, 59, a Catholic, was shot as he locked up his small station in the seaside village of Cushendall on the Co Antrim coast.
A police colleague was later acquitted of his killing, one of the most mysterious in the history of the violence in Northern Ireland.
Ms O'Loan has called in her own officers to make inquiries after claims by Sgt Campbell's family of security force collusion with loyalist paramilitaries.
The ombudsman declared: "Based on those inquiries, we feel that there are certain aspects of events before and after Sgt Campbell's murder which demand investigation.
"These are now the subject of a full investigation by my office."
In the 1990s the Campbell family called for an independent inquiry into the killing amid claims of security force collusion.
Ms O'Loan stressed that her officers would not be re-investigating the murder itself.
"There has been a lot of speculation about police involvement in the murder and this has caused a great deal of distress and anxiety to the Campbell family over the years.
"The speculation has been damaging to both the family and policing in Northern Ireland and it is in the interests of both that we do all we can to discover the truth about whether or not police misconduct played a part in this murder."
She warned Mr Campbell's family, his former colleagues and the people of Cushendall that the investigation would not be easy.
PA