What is the test for an allegation of bias against a tribunal?

“An allegation of bias, especially actual and not simply apprehended bias, against a tribunal is a serious allegation. It challenges the integrity of the tribunal and of its members who participated in the impugned decision. It cannot be done lightly. It cannot rest on mere suspicion, pure conjecture, insinuations or mere impressions of an applicant or his counsel. It must be supported by material evidence demonstrating conduct that derogates from the standard. It is often useful, and even necessary, in doing so, to resort to evidence extrinsic to the case. That is why such evidence is admissible in derogation of the principle that an application for judicial review must bear on the matter as it came before the court or tribunal” (Arthur v. Canada (Attorney General), 2001 FCA 223, at para.8). It cannot also rest on the statistics of the number of cases won by a counsel before a particular decider, since every case has its own particularities and the facts are never the same and depend, especially in this type of case, on the situation of each individual claimant.