The Garda Commissioner Drew Harris has apologised to the family of murdered prison officer Brian Stack.
Mr Stack - who worked at Portlaoise Prison - was shot in the neck by the IRA in Dublin in 1983 and died 18 months later.
His son, Austin, has previously accused the Gardaí of frustrating the inquiry into his murder.
He claims a past report by the Serious Crime Review Team found 194 errors in the original investigation, and that a final report is now before the commissioner.
Last year, the family claimed "significant information" had not been passed to the Garda team investigating the killing.
In a statement on Wednesday, Commissioner Harris says: "Along with senior detectives, I met with the Stack family this morning to provide them with a briefing on the ongoing investigation into the murder of Mr Brian Stack.
"I offered the Stack family an apology for the failings and shortcomings in the investigation.
"I fully acknowledge that these matters are serious and had a detrimental impact on the investigation.
"This investigation remains open and An Garda Síochána would appeal for anyone with information in relation to the murder of Mr Brian Stack to come forward."
The family of Brian Stack say they’ve received a verbal apology from the Garda Commissioner over “errors” which occurred during the investigation into his murder. The family now wants an independent policing expert to investigate the case. pic.twitter.com/yc22nhVKvR
— Shane Beatty (@ShaneBeattyNews) July 10, 2019
The Stack family is now urging the Justice Minister Charlie Flanagan to appoint an independent police expert to examine the case.
Mr Stack's son, Austin says they appreciate the Garda apology.
"It's actually quite significant that the Gardaí are, at this stage, now actually admitting that there were errors, admitting to the family that things that should have been done weren't done.
"I think it's quite right and proper that the commissioner would acknowledge that, and I would thank him for doing so".
