However, his caveat raises interesting questions about who else might be in a position to help the family and others in the communities affected. Adams is very unspecific on this: "but if they are not comfortable with that then let them go forward to a reputable body to get the family get where they want to be".

No doubt everyone will have their own theories about which reputable bodies will be. Amongst them may be a number of NGOs with good records in supporting people affected by crime within a community context. But none of them can replace a police force, in its capacity to clearly and accountably form prosecutions and see them through to court.

If, as many will suspect, the IRA is one of the reputable bodies Adams has in mind, it may come to be seen to be compromised on a number of counts. Not least that several of its (albeit lately disowned) members are accused of using their authority to conceal their own supposed guilt or complicity in the crime. But more fundamentally (and some of its members may grudgingly accept this), it is not a police force.

Ironically, the PSNI is now one of the most accountable police forces in the developed world. This is largley a result of sustained pressure on the part of the SDLP and Sinn Fein, with the purpose of enhancing the confidence of Nationalists in a comprehensive police force.

Will the party see out the pressure and continue to withhold its recognition of the PSNI as some kind of quid pro quo for the final exit of the IRA from Irish politics? Or will it recognise a vastly reformed police service and give practical support to the McCartney's or indeed others who may have suspended their own quest for justice?

The problem with the former is that it's value may have already fallen into serious negative equity. The risk of the latter could be the fragmentation of the movement. But as the dramatic fall in Adams's own popularity ratings shows, continued inaction has serious costs of its own.