When criticised for his Brian Stack murder "investigation", Gerry Adams has a standard response.
It gets a bit lost amid his petulant martyrdom, but he makes it as plain as he ever makes anything – topping and tailing his Dáil statement last week with it, for example.
That response is, to paraphrase: if you want a better process, others must agree a mechanism to deal with the past.
On Monday, Bertie Ahern said he understood the Sinn Féin president's position, adding that as taoiseach he had called for a "peace and truth commission".
In fact, a cross-border mechanism to deal with the past has been ready for the past two years. Its structure was agreed at the Stormont House talks in 2014 and its funding was agreed at the Fresh Start talks in 2015.
In terms of how this is meant to work, Adams’s behaviour makes perfect sense – or at least it is internally consistent.
Stormont House’s mechanism has three interlocking parts. The Historical Investigations Unit is a specialist police service that will take on all the PSNI’s Troubles legacy cases and pursue them fully, with a view to prosecutions if new evidence emerges. This is how bereaved families may seek justice.
The main hope of new evidence in old cases will be testimony from protagonists. This may be sought through the second part of the mechanism, the
on Information Retrieval. However, anyone who testifies to it is guaranteed anonymity, with their statements made inadmissible in criminal and civil courts.
So if the bereaved seek truth, they must forego justice.
The final part of the mechanism is the Implementation and Reconciliation Group, a panel of academics who will compile an official archive and narrative of the Troubles, assisted by metadata from the other two parts. So any protagonist cynically playing truth off against justice may damage history's judgement of their cause. Or maybe not; the panel will have an international chair but its 10 other members will be nominees from the Stormont parties and the British and Irish governments.
Everyone has agreed how many academics each can nominate – this is a system that has been worked out in remarkable detail, and it has a pedigree long enough to be seen as inevitable. A similar three-part mechanism was proposed by the 2009 Consultative Group on the Past, Northern Ireland's first attempt to address this issue.
So what is the hold-up? The British and Irish governments are joint stewards of the Stormont House system, with a further sign-off required from Sinn Féin and the DUP as the two executive parties.
The point on which everyone has fallen out is disclosure to the Historical Investigations Unit. Both governments promised “full disclosure”, only for London to qualify this on grounds of national security.
Nationalists have cried foul, with Dublin also now voicing frustration. The British government has replied that states keep records while terrorists do not, so there is an imbalance in the system. This is a standard unionist response and also not a direct answer to nationalist objections, so a dialogue of the deaf has ensued.
Many bereaved families suspect it would suit all sides to drag this out indefinitely. But Adams’s approach to the Stack family shows that even if agreement was reached, it will still prove a crushing disappointment.
When Stack’s sons approached Sinn Féin for help they were effectively put through the Stormont House mechanism, by being given a choice between truth or justice. The IRA’s truth left them still wanting justice. As a result, everyone is now arguing over the narrative.
How many times would this recur under a formal mechanism, with 3,500 murders to address?
It turns out that people cannot be forced to choose between seeking confessions or seeking convictions.
Human rights standards and the integrity of the legal system itself mean proper investigations, prosecutions and trials must always be an option – even after an alternative process as exhaustive as the Bloody Sunday Inquiry. Many relatives expect no less and all must be entitled to it.
During the 2015 on-the-runs scandal, it emerged that the British government had offered around 200 IRA suspects a de facto Troubles amnesty.
The scheme collapsed once exposed because an actual amnesty is impossible, as subsequent legal and political debate made clear.
The choice imposed on families by the Stormont House mechanism is an attempt to reflect this – but the Stack case shows how imperfect it is if the victims do not play along.
Instead of asking Adams why he was driving a blacked-out van across the Border, he should be asked why Sinn Féin supports certain campaigns for truth and justice while demanding a general approach of truth or justice.
If he has found a way to reconcile those objectives, the whole of Ireland could usefully hear it.