Just as the public inquiry into the death of Rosemary Nelson in 1999 is opening, serious questions are being asked about collusion in the murder of RUC constable John Larmour in 1988, killed by the IRA in a Belfast ice-cream parlour. Dealing with the past, in ways that provide some closure for relatives, is proving a lengthy, costly and far from satisfactory process.
Mr Larmour's son, Gavin, has failed to get the PSNI to re-open the case, although in an earlier investigation the then Police Ombudsman, Nuala O'Loan, found that police had information which, if acted upon, might have identified the murderer.
"More thoroughness would have been expected in follow-up inquiries," she said, noting that the killer's gun had been used in previous attacks and that detectives had been hampered in their original investigation.
Where there is evidence of the police's reluctance to produce relevant information, there must be a suspicion that there is something to hide — and possibly that an informer is being protected. It has to be remembered how vital intelligence-gathering was to combating terrorism, but nowadays the priority is different.
Victims' families deserve to hear the truth, even if it causes embarrassment to people in high places.
Collusion is never easy to deal with, and it is particularly repugnant in cases where it might involve the murder of a member of the security forces, like Constable Larmour. There are limits to the protection of any individual within a paramilitary organisation, and they certainly do not extend to allowing anyone the freedom to murder.
The Nelson case is another which has been subject to several investigations, over the years, and the public inquiry is a means of allowing a three-person judicial panel to hear all the witnesses and conclude whether collusion was a factor or not.
What made this car-bomb murder different was that it involved a high-profile solicitor, representing republicans and objectors to the Drumcree marches, who herself warned the authorities here, in Washington and the United Nations that she was being targeted. She even said she had been threatened by members of the RUC, although these allegations were denied.
The murder, which was claimed by the Red Hand Defenders, a cover name for the UDA and the LVF, involved an unusually sophisticated mercury tilt device, attached to her car. Since the leadership of these organisations was generally known, being on display at Drumcree, were the police's inquiries sufficiently thorough?
Public inquiries have yet to prove their worth, to victims' families, and they have been an enormous financial burden on the state.
Meanwhile the victims commissioner appointments are in danger of turning into a long-running farce and the Eames-Bradley panel's job of "dealing with the past" is clearly a minefield.
Yet we must learn from the past, to secure a better future.