The Minister’s common retort that making findings as to credibility is a task of the tribunal ‘par excellence’ is often abused. That tautology does not mean that credibility findings cannot be challenged in judicial review. Criticism of the abuse of ‘par excellence’ was made in CQG15 v Minister for Immigration and Border Protection  FCAFC 146 at -:
Before considering the arguments in detail, there is one topic which this appeal usefully highlights. That credibility is a matter par excellence for the Tribunal is an expression often used. It stems from Minister for Immigration and Multicultural Affairs; Ex parte Durairajasingham  HCA 1; 74 ALJR 405 per McHugh J. At - his Honour, sitting in the High Court’s original jurisdiction as a single judge, said (footnotes omitted):
67 In addition, the prosecutor alleges that the Tribunal breached s 430(1) by failing to set out reasons for its finding that the prosecutor’s claim that members of PLOTE tried to recruit him were “utterly implausible”. However, this was essentially a finding as to whether the prosecutor should be believed in his claim – a finding on credibility which is the function of the primary decision maker par excellence. If the primary decision maker has stated that he or she does not believe a particular witness, no detailed reasons need to be given as to why that particular witness was not believed. The Tribunal must give the reasons for its decision, not the sub-set of reasons why it accepted or rejected individual pieces of evidence. In any event, the reason for the disbelief is apparent in this case from the use of the word “implausible”. The disbelief arose from the Tribunal’s view that it was inherently unlikely that the events had occurred as alleged.
68 But there is a more fundamental reason why the argument based on s 430 fails to support a claim for prerogative relief. Even if, contrary to my view, there was a breach of s 430(1) by the Tribunal, it would not amount to a jurisdictional error. In Minister for Immigration and Ethnic Affairs v Eshetu, Gummow J referred to the requirement that, before granting a protection visa, the Minister and, on review, the Tribunal be “satisfied” that the prosecutor was a refugee. That requirement arose from ss 36 and 65 of the Act. His Honour said:
“A determination that the decision-maker is not ‘satisfied’ that an applicant answers a statutory criterion which must be met before the decision-maker is empowered or obliged to confer a statutory privilege or immunity goes to the jurisdiction of the decision-maker and is reviewable under s 75(v) of the Constitution.”
The prosecutor argued at the hearing that s 430(1)(c) “feeds into the ascertainment of the Minister’s satisfaction” and that it is “an integral part of ascertaining the jurisdictional fact”.
It is important to note that McHugh J’s observations and his Honour’s use of the phrase “par excellence” were made in the specific context of a claim that the Tribunal had not complied with its statutory obligation under s 430 of the Migration Act to give reasons for its decision. Nothing said by McHugh J suggests that the Tribunal’s adverse findings on credibility are not amenable to judicial review on jurisdictional error grounds. There is a risk that a mechanical use of the phrase “par excellence” as a formula fails sufficiently to appreciate this important reality. The fact that credibility is a matter for the Tribunal to determine as a question of fact does not mean that challenges to credibility are not open. This appeal illustrates three of a number of potential bases of challenge to credibility findings on well‑established legal precedent. In the present appeal, the foundation for the challenge is on the basis of no logical or probative basis for the finding in relation to ground 1, illogicality and/or irrationality in relation to ground 2, and, in relation to ground 3, a lack of natural justice.
There are several other potential bases upon which credit findings can be challenged. Recitation of the expression that credibility is a matter par excellence should not be understood as precluding challenges to credibility or, indeed, other findings of fact on any basis. While there is no suggestion in this case that this is what has occurred, the frequency of adoption of the expression should not obscure the availability of challenges on recognised grounds, such as:
(a) failure to afford procedural fairness;
(b) reaching a finding without any logical or probative basis;
(c) unreasonableness; and/or
(d) jurisdictional error as discussed by Flick J in SZVAP.