The latest phase of the penalty points affair is coming to a head rapidly. A serving Garda sergeant is due to tell the Public Accounts Committee today or tomorrow whether he is willing to appear before it on Thursday to set out his concerns about the matter. In question already is whether Garda commissioner Martin Callinan asks the courts to block any such hearing.

PAC members were told around noon today to attend a private meeting of the committee in Leinster House tomorrow at 4pm. It should then be clear whether the Garda sergeant, who has been taking legal advice, is willing to appear. If he is, says PAC chairman John McGuinness, then the only question for the PAC to settle is whether the hearing goes on in public glare or in private. Or is it?

Not so fast, say some PAC members. In the face of a possible legal challenge to any such hearing by Mr Callinan, some TDs on the committee say it should proceed with absolute caution. The principal anxiety is legal advice to the PAC itself from its own expert that it risks straying beyond its formal remit.

Mr McGuinness insists the committee is doing nothing of the sort, saying it is acting strictly in line with its mandate and adding that the Comptroller & Adusitor General has also looked into the penalty points question.

In one line of argument, there would be nothing improper in a hearing which simply confines itself to issues related to the loss of State revenues due to the cancellation of penalty points and the associated fines. But if this raises claims about the alleged abuse of Garda powers, questions might well be asked as to the adequacy of the PAC examination if it does not delve into that matter. The question is etiher relevant to the inquiry or it is not. If it is, then it should be examined fully.

While Garda authorities insist there is no basis at all for the abuse of power claims, Mr Callinan goes further by saying the PAC should not be the forum to investigate them. On the strengthof his own remarks to the PAC last week, a legal challenge must at this point seem more likely than not.

No matter what Mr McGuinness says, there is real concern among TDs on the PAC that it would not be able to withstand a court challenge from the Garda commissioner in light of the committee’s own legal advice. How could the PAC persuade a judge to allow it to hear evidence from a serving Garda if the committee’s own adviser warns of mission creep beyond its own powers?

All of this may soon be played out in open court. Whether it casts any light on what really went on within the Garda in relation to penalty points is another matter.

If the arugment of the moment centres on the notion of a parliametary committee supposedly preoccupied with financial matters investigating alleged police wrongdoing, the wider political question centres on the dubious idea of gardaí investigating gardaí. The reforms introduced in the wake of the Morris tribunal were supposed to settle that question for once and for all. Not so.