R. v. Nero, 2016 ONCA 160:
...bias must be reasonable, held by reasonable and right-minded persons applying themselves to the question and obtaining the required information about it. The test is "what would an informed person, viewing the matter realistically and practically – and having thought the matter through – conclude": Committee for Justice and Liberty v. National Energy Board,  1 S.C.R. 369, at p. 394; R. v. R.D.S.,  3 S.C.R. 484, at para. 111; Wewaykum Indian Band v. Canada, 2003 SCC 45,  2 S.C.R. 259, at para. 60.
 Second, the standard refers to an apprehension of bias that rests on serious grounds in light of the strong presumption of judicial impartiality: Committee for Justice and Liberty, at p. 395; Wewaykum, at para. 76. The grounds for the apprehension must be substantial: R.D.S., at para. 112.
 Third, as a necessary consequence of the presumption of judicial impartiality, the onus of demonstrating bias lies with the party who alleges its existence: R.D.S., at para. 114. That party must prove bias on a balance of probabilities: Marchand (Litigation Guardian of) v. Public General Hospital Society of Chatham (2000), 51 O.R. (3d) 97 (C.A.), at para. 131
 Fourth, the inquiry into a reasonable apprehension of bias is fact-specific. Said in another way, whether a reasonable apprehension of bias arises, all the more so whether it has been established, depends entirely on the circumstances of the case under consideration: R.D.S., at para. 114.
 Finally, at least as a general rule, allegations of bias or a reasonable apprehension of bias should be advanced as soon as it is reasonably possible to do so: R. v. Curragh Inc.,  1 S.C.R. 537, at para. 11.