There is a brief summary of the authorities on when discourteous behaviours of RRT members can amount to a denial of natural justice by reason of apprehended bias, in AZAEY v Minister for Immigration and Border Protection  FCAFC 193.
On the facts in AZAEY, there was no apprehended bias. This was so, even though the Court found that on some occasions the Tribunal member did interrupt the Applicant on ‘a number of occasions’, was ‘incredulous’ towards the Applicant and raised her voice towards the Applicant. The Court also referred to a number of occasions in which the Applicant was crying, presumably as a result of the Tribunal member’s behaviour.
The Court concluded however, that when having regard to the transcript and recording of the RRT hearing as a whole, an informed person ‘would satisfactorily reach a conclusion that the Applicant had been afforded a hearing in which the Tribunal member was “open to persuasion”‘: . That is the ‘governing principle’ in relation to apprehended bias: see Ebner v Official Trustee in Bankruptcy  HCA 63, (2000) 205 CLR 337 at 344 to 345, cited in AZAEY at .