The Garda smearing of a murdered man's name ranks among the most shameful episodes of the Irish state, Dublin's High Court has been told.
A barrister said the Justice Minister's failure to hold a commission of investigation into events around the 1976 killing of Seamus Ludlow "flies in the face of reason" when such an inquiry was being considered for the Olympics ticket-touting affair.
Summing up a three-day hearing, the first time the case has been heard in a court, Ronan Lavery QC, for the family, said the gravity of the allegations involved demanded a proper inquiry.
"The failure in conduct of gardai after the killing, in smearing Seamus Ludlow's name, must rank among one of the more shameful episodes that could be laid at the door of the state," he said.
"It is not just in the interest of the Ludlow family to look at this, but it is in the interests of every citizen to examine this closely."
Mr Ludlow, a 47-year-old bachelor, was shot dead as he was returning home to Mountpleasant, Dundalk, from a pub in the Co Louth town on May 2, 1976.
His family say gardai were behind a smear campaign wrongly alleging the murder was carried out by the IRA because Mr Ludlow was an informer and that some family members had prior knowledge it was planned, sparking a decades-long rift among them.
A parliamentary committee in Dublin recommended more than 10 years ago that two commissions of investigation be held into the murder and subsequent events, after an official judge-led report damned the original botched Garda probe.
The Ludlow family is seeking a High Court declaration that the justice minister's failure to launch an inquiry is unlawful.
The Royal Ulster Constabulary told the Garda in 1979 the names of four loyalists it suspected of being involved in Mr Ludlow's killing, but the information was not pursued by the Garda at the time.
The family was told by a local garda that the murder probe was suspended without explanation three weeks after it started on orders that "came from Dublin", the court has heard.
No one has ever been charged with the murder.
Two of the suspects were members of the Ulster Defence Regiment, a now defunct unit of the British Army.
"If this is not a serious matter of public concern one cannot imagine what is," Mr Lavery told the High Court.
Justice Mary Faherty said every matter that comes before the High Court is weighty and this case was particularly weighty.
Reserving her judgement, she said she would take some time to consider the documents and reread the original parliamentary committee report.
Solicitor for the Ludlow family, Gavin Booth of KRW law firm in Belfast, said outside the court it was unfortunate the family "had to take these steps".
"But it is important that justice is done and seen to be done," he said.
"Every day the Taoiseach and Minister for Justice delay, it causes further grief and distress for a family that has been through so much at the hands of the state."