Here are some of the key findings Police Ombudsman Marie Anderson’s examination of the RUC’s handling of the Kingsmill Massacre investigation.
The ombudsman detailed several instances of police planning to arrest suspects but not following through.
She also expressed concern over a failure to arrest a number of individuals who had been linked to the attack in information received by the RUC in late 1976 which named 11 suspects.
“The unexplained failure to exploit the evidential opportunities that may have been offered by the prompt arrest and interview of these individuals undermined the potential development of further lines of inquiry,” she said.
More than 150 ballistic exhibits were recovered from the scene of the murders, with police establishing that 11 weapons were used by the gunmen.
These weapons were linked to a series of attacks carried out by republican paramilitaries both before and after Kingsmill, but the ombudsman found no evidence of police utilising those linkages in the investigation.
A hijacked minibus used by the attackers was found abandoned across the border in Dundalk following the shooting.
The ombudsman said Irish police recovered nine exhibits from the minibus however only five of those samples were subsequently submitted for examination by the RUC. She found no explanation for that.
Ms Anderson said there were no records showing the outcome of those forensic tests and the samples cannot be traced.
The ombudsman also highlighted several failures in linking a palm print found on the getaway vehicle to a suspect.
“I believe the original police investigation failed to properly consider the value of the palm print from the minibus which was probably used to facilitate the movement of the killers before and after the Kingsmill attack,” she said.
The ombudsman questioned why a threatening call made a week prior to the attack to two workers employed in the same mill as the victims was not further investigated by police.
Ms Anderson also identified gaps in witness inquiries by the RUC officers at the time and raised concerns that several documents related to the investigation have gone missing in the decades since.
The ombudsman’s probe found no intelligence that could have forewarned police of the Kingsmill attack or allowed officers to prevent it and did not identify any intelligence that indicated a direct threat to any of the victims.
She said following the attack, police received specific intelligence identifying named individuals and their roles in the attack, indicating that the shooting had been planned some weeks before it took place.
Ms Anderson said that contradicted a widely held view that the attack was a “spontaneous response” to the murders of several members of two Catholic families in the area on the day before.
In assessing the evidence available to police, the ombudsman added: “My investigation has not seen any evidence that was available to the investigation team which would have led to the conviction of any person for the offences of murder and attempted murder.”
Ms Anderson stressed that she had no remit to investigate the conduct of military personnel in the area at the time.
However, she did find there was no evidence that soldiers were intentionally kept away from the area, or instructed to avoid it, on the night of the attack.
She said there was also no evidence of any covert police or military operations ongoing at the time.
