The Ombudsman, Marie Anderson, also detailed other “missed” investigative opportunities in the probe into the killings of 18-year-old Seamus Morris and Peter Dolan (25) in north Belfast on August 8.
On the day of the murders, a taxi had been hijacked in the Shankill area and driven to Ardoyne. On Etna Drive, a gunman opened fire from a passing taxi, killing Mr Morris, who was crossing the road with his brother.
Moments later, Mr Dolan was killed when the gunman fired at him as he sat in a lorry at nearby Brompton Park.
Neither victim was connected to any paramilitary organisation. The Police Ombudsman launched an investigation following a complaint from the family of Mr Morris filed a decade ago.
A VZ58 rifle, one of a batch imported into Northern Ireland by loyalist paramilitaries, was used in the double murder.
It was recovered by the RUC in September 1988 and incorrectly linked to three murders in the Avenue Bar in May 1988.
It was only years later when ballistic evidence from all recovered VZ58 rifles was re-examined that the rifle found in September 1988 was linked to the murders of Mr Morris and Mr Dolan.
“The failure to correctly link the VZ58 rifle, at the point it was recovered by police in 1988, to the murders of Mr Morris and Mr Dolan deprived RUC investigators from developing lines of enquiry and interviewing suspects,” Ms Anderson said.
“Equally, the incorrect link made between this weapon and the murders at the Avenue Bar may also have hindered that police investigation.
“This misattribution of weapons to murders, by the RUC’s Weapons and Explosives Research Centre and/or the Northern Ireland Forensic Science Laboratory, was highlighted to PSNI as a potential systemic issue.
“However, it is not known the extent to which murder investigations involving the use of VZ58 assault rifles may have been misdirected in consequence of these errors.”
The Ombudsman’s investigation also found that six months before the two murders, the RUC had intelligence that the UVF was storing rifles at a specific social club in north Belfast.
Intelligence received said that some firearms had been moved from the social club to the Shankill and Ballysillan areas, including to the address of a suspected UVF member who was later arrested for the murders of Mr Morris and Mr Dolan.
Police also had information that the social club had been used for paramilitary displays, meetings of the UVF’s B company in north Belfast and other serious crimes.
Two men active at the social club were implicated through intelligence as being involved in the double murder.
Despite the RUC’s intelligence regarding the social club, Ms Anderson said her probe could not find any evidence that police investigated the intelligence or carried out “disruptive tactics” regarding UVF activities at the social club prior to the murders of Mr Morris and Mr Dolan.
Two people were arrested following the murders. One of the suspects was linked to the UVF through intelligence and to the storage of weapons, but there was no evidence that the alibi he gave was checked.
In 2008, it was established that a fingerprint found in the stolen taxi used in the murders matched a suspected UVF member.
Ms Anderson questioned why this match wasn’t made in 1988, when police compared the fingerprint to those of a list of known paramilitaries, including the suspected UVF member.
Mr Morris’ brother gave police a description of one of those in the taxi, but Ms Anderson said there was no evidence he was shown pictures of any suspects, or asked to view an identification parade.
Ms Anderson said: “I believe that Mr Morris and Mr Dolan were the innocent victims of a campaign of sectarian violence mounted against the nationalist community.
“Loyalist extremists were responsible for their murders. However, given the investigative failings and omissions identified, I believe that the Morris family were failed by police in their search for accountability for the murders of their loved one.”
The Morris family had complained that collusion was a feature in the murders.
Ms Anderson referred to a recent Court of Appeal judgment regarding her powers to make such a determination.
“Although the family have complained about collusion between the security forces and those who murdered Mr Morris and Mr Dolan, I am not permitted to express any view of my own on this issue, in consequence of a recent High Court judgment,” she said.
“The detailed narrative outlined in this public statement of the circumstances of Mr Morris’ murder must be read in the context of that judgment and in light of my obligations under Article 2 of the European Convention to provide an independent and fulsome investigation of the family’s complaints.”