It’s simple - do you believe Mr ‘I wasn’t in the IRA’ or don’t you?
It's not a particularly tough call, this one. We are being asked to choose between Austin Stack, son of murdered prison officer Brian Stack, and one Gerard Adams, president of Sinn Féin.
The Stack family have campaigned for 30 years for some form of recognition for their husband and father, who was a senior prison officer in Portlaoise Prison at a particularly fraught time in Irish history.
It has been a very hard and lonely road for them, and for a long time their story did not fit with contemporary politics in a changing Ireland amid a quest for some resolution in Northern Ireland.
As the only prison officer in the Republic murdered during what we euphemistically call the 'Troubles', his story could be relatively easily downplayed.
Those familiar with the 1996 killing of Garda Jerry McCabe will see comparisons.
It was expressly forbidden to fire upon a serving member of the security forces in the Republic.
So, there were perfunctory official denials by the IRA in both cases.
These denials later morphed into grudging acceptance they were "unsanctioned operations" and various other forms of weasel words which strain the concept of truth.
Meanwhile, Sinn Féin, which has links with the IRA of the 1970s and 1980s that are personified inside Leinster House, leads the charge for full disclosure and justice for all IRA personnel killed in dubious circumstances by various security forces.
But let's return to our departure point, and focus in on who we might believe in the recounting of a bizarre series of events in 2013 and subsequently.
The major conflict in the two divergent accounts is that Gerry Adams insists that Austin Stack and his brother, Oliver, first told him the identity of their father's killers. Mr Adams says they got their information from security journalists and Garda sources. Not so, insists Austin Stack, who believes the IRA wanted to kill their father to further a major outbreak from Portlaoise Prison.
Austin Stack says he never gave those names to Gerry Adams.
Curiously, the four names occur in an email dashed off by Mr Adams to the Garda Commissioner Nóirín O'Sullivan just days before polling in the Irish general election in February.
That brings us to another conflict in the Sinn Féin account of events.
Just days ago, Mr Adams' deputy, Mary Lou McDonald, said she believed that Mr Adams had given all the information he had without delay.
But this is not in accord with Mr Adams' recall.
The bulk of Adams-Stack contacts - including the surreal journey in a blacked-out van to a locale near the border - occurred in summer 2013, two-and-a-half years earlier.
Recalling that strange encounter with "a senior IRA figure" raises another point. Just who is this person? Mr Adams, challenged by the Taoiseach to avail of Dáil privilege to tell all he knew, notably failed to help us on this matter.
The mystery IRA informant upheld the tradition of telling the Stacks their father's killing was not "officially sanctioned".
The renegade who did the killing was subsequently "sanctioned".
We know not who that renegade is and we have no idea what the "sanction" amounted to. But an IRA kangaroo court is another travesty unto itself.
The email which Mr Adams sent Commissioner O'Sullivan before the last election included the names of four people who may have information about the unsolved murder.
Mr Adams said he had spoken to three of those four people, but made it clear in the email that he had no information on the killing.
"There is a live Garda investigation. I am prepared to cooperate with this," Mr Adams told the Dáil, slipping easily into the role of the man here to help.
It was an unusual opportunity afforded Mr Adams to make a personal statement in the Dáil on the Stack murder and the attendant controversy.
But it came after repeated questions from the Taoiseach Enda Kenny and Fianna Fáil leader Micheál Martin.
On the killing, Mr Adams oozed sympathy and concern.
"It was a grievous loss for his family and should never have happened," he said.
But he also defended the anonymity given to former IRA members who supported the peace process and those who worked to recover the bodies of the IRA's Disappeared victims.
And he defended the same approach of anonymity for IRA members involved in decommissioning, the Smithwick Tribunal, secret talks with governments and ceasefires.
"Progress was only possible on the basis of confidentially and trust. That is why no IRA people were named during any of these initiatives and why they should not be named today," he said.
"It is an essential part of any conflict resolution process."
So, it was an easy walk from there to cue his own role as honest broker, trying out of compassion to help the Stack family.
He was not acting out of political convenience, and trying to forestall controversies which could damage his party's political progress in the Republic. Perish that unworthy thought.
The big problem is that Mr Adams has given so little past reason to believe he really cares about people such as the Stacks, who have had to carry 30-plus years of grief and sorrow.
For the longest time he remains insistent he never was in the IRA. That comes in spite the view of all heavy hitting politicians in these islands - and the security forces in at least three jurisdictions.