Northern Ireland's Police Ombudsman is investigating "possible police misconduct" by members of the Royal Ulster Constabulary before and after the murder of a Catholic colleague.
A spokesman for Nuala O'Loan confirmed her team of investigators was looking at the circumstances surrounding the murder of Sergeant Joseph Campbell outside a police station in the seaside resort of Cushendall.
In one of the most controversial murders of the Troubles, 49-year-old Sergeant Campbell was shot with a rifle as he locked up the small RUC station in the County Antrim village on February 25, 1977.
He was married with eight children.
Sergeant Campbell's family and human rights campaigners believe he was a victim of collusion between members of the security forces and the loyalist paramilitary group the Ulster Volunteer Force.
They have passed fresh information to Mrs O'Loan's office, which oversees the actions of the Police Service of Northern Ireland and its predecessor, the Royal Ulster Constabulary.
A spokesman for Mrs O'Loan said: "Sergeant Joseph Campbell was shot dead on the night of February 25, 1977 as he locked up the small RUC station at Cushendall on the Antrim coast.
"An RUC officer, who was arrested and charged with his murder, was later acquitted of Mr Campbell's death. Earlier this year, Mr Campbell's family made a number of complaints to us and presented us with fresh information which has not previously been investigated.
"We carried out a preliminary investigation. As a result of that fresh information, we are now investigating certain aspects of events before and after the murder which relate to possible police misconduct.
"We are not, as yet, investigating Sergeant Campbell's murder but only the circumstances surrounding it."
PA