The detective who led the investigation into the Kingsmills murders has apologised to the victims’ families for not getting the satisfaction they hoped for.
Det Ch Insp Mitchell said the “workload at the time” and “depleted resources” led to weaknesses in the investigation.
Ten Protestant men were shot by the IRA in the attack known as the Kingsmills massacre in County Armagh in 1976.
They were shot after gunmen stopped their bus on their way home from work.
During questioning by a barrister for one victim’s family, Det Ch Insp James Mitchell acknowledged that forensic evidence from a van that was involved in the murder was not correlated with evidence found at the scene.
If the evidence had been correlated it would have enabled detectives to place the van at the scene, but that did not happen.
Samples of soil, a broken mirror and paint were taken by the forensics team from the scene.
Forensic evidence was also gathered from a dark green van which had been hijacked earlier and discovered across the border in Dundalk, County Louth.
During the eight months after the killings no forensic reports relating to those items removed were received by the investigations team.
This was despite the fact that a positive match between the two sets of evidence could have proven that the van found in Dundalk was at the scene of the massacre.
The HET investigation established that no evidence remained.
It also said that some of the original evidence had been destroyed in a fire at the laboratory eight months after the killings.