This is not the first time that I have blogged about credibility, but I re-iterate that (adverse) credibility findings are the bane of the applicant lawyer’s life. The main reason is that usually (there are exceptions) an adverse credibility finding by a delegate is a finding of fact and can’t be judicially reviewed.
The reverse problem occurred in ABT17 v Minister for Immigration and Border Protection  HCA 34 where although the protection visa applicant was unsuccessful (because the country information for Sri Lanka indicated there was low risk to him), his story had been found plausible by the delegate who interviewed him. That finding of (positive) credibility was reversed by the review authority who only listened to an audio recording of the interview. Although all the High Court judges allowed the appeal, there were some differences in reasoning.
The majority view was that it was effectively legally unreasonable for the review authority to reverse the credibility finding (at least without conducting a further interview).
The judgment of Nettle J (starting at ) sets out the procedural history and summarises some useful authorities about the role of appeal bodies (around +) and raises an administrative law elephant in the room – the role of materiality in the law of unreasonableness. It’s fairly clear procedural unfairness has to be material, but it’s not so clear for unreasonableness. In fact there is a whole separate academic controversy on this point which is discussed by UNSW academic Lisa Crawford in her blog post – https://auspublaw.org/2020/10/how-should-a-court-respond-to-an-immaterial-error-of-law/
There were other lurking issues about whether it was actually within power for the review authority to conduct a new interview because it’s power was limited to considering only “new evidence” and it’s unclear whether a second interview would fall into that category.
This is really another one of those cases where the outcome was good for the applicant but it raises a number of other unresolved legal issues.