Bias and Intervention from the Bench. Uribe v. Tsandelis
In Uribe v. Tsandelis (Ont CA, 2021) the Court of Appeal set out the circumstances that allow, and the procedures for, a judge's questioning a witness:
 A trial judge is entitled to question witnesses for clarification by intervening in the testimony of witnesses. In Chippewas of Mnjikaning First Nation v. Ontario, 2010 ONCA 47, 265 O.A.C. 247, at paras. 231, 238 and 243, leave to appeal refused,  S.C.C.A. No. 91, this court considered questioning by a trial judge:. Younis v. Canada (Immigration, Refugees and Citizenship)
An examination of whether a trial judge has unduly intervened in a trial must begin with the recognition that there are many proper reasons why a trial judge may intervene by making comments, giving directions or asking questions during the course of a trial. A trial judge has an inherent authority to control the court's process and, in exercising that authority, a trial judge will often be required to intervene in the proceedings. The trial judge here followed the protocol referred to by this court said in R. v. Danial, 2016 ONCA 822, at para. 5:
On occasion, trial judges may be required to play a more active role in asking witnesses questions. However, when they do, it is important that they use care and not create an impression through the questioning process of having adopted a position on the facts, issues or credibility.
All of that said, appellate courts are reluctant to intervene on the basis that a trial judge "entered the arena" and improperly intervened in a trial. There is a strong presumption that judges have conducted themselves fairly and impartially. … In the end, an appellate court should only intervene if satisfied that the trial judge's interventions, considered in the context of the entire trial, created a reasonable apprehension that the trial judge was biased.
A trial judge is entitled to ask questions for clarification. The trial judge here followed the long standing protocol articulated in R. v. Stuckey, 2009 ONCA 151 at para 64. He waited until the conclusion of the witness’ testimony, asked questions for clarification on a narrow issue, and allowed further re-examination. That some of the questions towards the end of the series of questions may have been leading would not lead a reasonable observer being apprised of all the facts to conclude that the trial judge was not impartial. Questions by a trial judge may be problematic when they either disclose bias or lead to trial unfairness. There is a presumption of impartiality on the part of a trial judge and the trial judge’s questions do not disclose bias. Apprehension of bias was not alleged by the appellant.
In Younis v. Canada (Immigration, Refugees and Citizenship) (Fed CA, 2021) the Federal Court of Appeal considered an issue of bias:
 In Miglin v. Miglin, 2003 SCC 24, the Supreme Court of Canada confirmed the test for bias:. R. v. Gager
 The appropriate test for reasonable apprehension of bias is well established. The test, as cited by Abella J.A., is whether a reasonable and informed person, with knowledge of all the relevant circumstances, viewing the matter realistically and practically, would conclude that the judge's conduct gives rise to a reasonable apprehension of bias: R. v. S. (R.D.), 1997 CanLII 324 (SCC),  3 S.C.R. 484, at para. 111, per Cory J.; Committee for Justice and Liberty v. National Energy Board, 1976 CanLII 2 (SCC),  1 S.C.R. 369, at pp. 394-95, per de Grandpré J. A finding of real or perceived bias requires more than the allegation. The onus rests with the person who is alleging its existence (S. (R.D.), at para. 114). As stated by Abella J.A., the assessment is difficult and requires a careful and thorough examination of the proceeding. The record must be considered in its entirety to determine the cumulative effect of any transgressions or improprieties. […] In Yukon Francophone School Board, Education Area #23 v. Yukon (Attorney General), 2015 SCC 25, (Yukon) the Supreme Court of Canada noted:
 The inquiry into whether a decision-maker's conduct creates a reasonable apprehension of bias, as a result, is inherently contextual and fact-specific, and there is a correspondingly high burden of proving the claim on the party alleging bias: see Wewaykum, at para. 77; S. (R.D.), at para. 114, per Cory J. As Cory J. observed in S. (R.D.): As noted by this Court in ABB Inc. v. Hyundai Heavy Industries Co., 2015 FCA 157, at para. 55: "“[t]he onus of establishing a reasonable apprehension of bias lies with the person who alleges it, and the threshold for perceived bias is high”" (see also R. v. R.D.S., 1997 CanLII 324 (SCC),  3 S.C.R. 484, at para. 114, 151 D.L.R. (4th) 193, and Miglin, at para. 26). In this case, the onus is on Ms. Younis to demonstrate that the Judge was biased or that there was a reasonable apprehension of bias.
... allegations of perceived judicial bias will generally not succeed unless the impugned conduct, taken in context, truly demonstrates a sound basis for perceiving that a particular determination has been made on the basis of prejudice or generalizations. One overriding principle that arises from these cases is that the impugned comments or other conduct must not be looked at in isolation. Rather it must be considered in the context of the circumstances, and in light of the whole proceeding. [Emphasis added by the Supreme Court; para. 141.]
 Tense exchanges between a judge and counsel, even if the judge’s statements are discourteous, do not necessarily lead to a conclusion that a judge is biased. As noted by the Supreme Court in Miglin:
 […] We see no reason to interfere with the Court of Appeal's assessment of the record, nor with its conclusion that although the trial judge's comments were intemperate and his interventions at times impatient, they do not rise to the level necessary to establish a reasonable apprehension of bias. Similarly, the Ontario Court of Appeal in Stuart Budd & Sons Limited v. IFS Vehicle Distributors ULC, 2016 ONCA 60, (Stuart Budd) noted:
 It is important to acknowledge from the outset that it takes much more than a demonstration of impatience with counsel or even unwarranted discourtesy to rebut the strong presumption of impartiality: Kelly v. Palazzo, 2008 ONCA 82, 89 O.R. (3d) 111, at para. 21. The Nova Scotia Court of Appeal also noted, "“[m]omentary friction is not bias”" (2446339 Nova Scotia Ltd. v. AMJ Campbell Inc., 2008 NSCA 9, at para. 105).
 However, courts will be rightly troubled when a motion judge is consistently discourteous towards counsel for no apparent reason. Derisive remarks will therefore be relevant to the issue of bias: see Yukon, at para. 52.
In R. v. Gager (Ont CA, 2020) the Court of Appeal reviewed some principles of bias, especially regarding intervention by the judge:
(b) Reasonable Apprehension of Bias. R. v. Chambers
 Because of the strong presumption of judicial fairness, impartiality and integrity that is not easily displaced, there is a high burden on the party alleging bias to prove on the basis of substantial grounds that there is a real likelihood or probability of the appearance of bias: Yukon Francophone School Board, Education Area #23 v. Yukon (Attorney General), 2015 SCC 25,  2 S.C.R. 282, at para. 25; Miglin v. Miglin (2001), 2001 CanLII 8525 (ON CA), 198 D.L.R. (4th) 385 (Ont. C.A.), at paras. 29-30, rev’d on other grounds, 2003 SCC 24,  1 S.C.R. 303. As I explain, I am of the view that the appellants have fallen far short of this stringent threshold.
 The well-known test for establishing a reasonable apprehension of bias, as first articulated by the Supreme Court of Canada in Committee for Justice and Liberty et al. v. National Energy Board et al., 1976 CanLII 2 (SCC),  1 S.C.R. 369, at p. 394, per de Grandpré J. (dissenting), is as follows:
[W]hat would an informed person, viewing the matter realistically and practically – and having thought the matter through – conclude. Would he think that it is more likely than not that [the trial judge], whether consciously or unconsciously, would not decide fairly. As the Supreme Court confirmed in Yukon Francophone School Board, at para. 22: “The objective of the test is to ensure not only the reality, but the appearance of a fair adjudicative process” (emphasis in original).
 While a judge’s conduct, particularly his or her interventions, can rebut the presumption of impartiality, a judge’s individual comments or interventions must not be seen in isolation. Rather, the impugned conduct must be considered in the context of the circumstances and in the light of the whole proceeding. The inquiry is therefore inherently contextual and fact-specific: see Yukon Francophone School Board, at paras. 25 to 27.
 As Mr. Gager’s counsel on this appeal fairly acknowledged, the appellants would not likely have raised the issue of reasonable apprehension of bias solely on the basis of the trial judge’s alleged verbal interventions, as most of them were justified as being within his case management prerogative as trial judge. This is consistent with the comments of Lamer J. in Brouillard Also Known As Chatel v. The Queen, 1985 CanLII 56 (SCC),  1 S.C.R. 39, at p. 44:[I]t is clear that judges are no longer required to be as passive as they once were; to be what I call sphinx judges. We now not only accept that a judge may intervene in the adversarial debate, but also believe that it is sometimes essential for him to do so for justice in fact to be done. Thus a judge may and sometimes must ask witnesses questions, interrupt them in their testimony and if necessary call them to order.
 As Mr. Gager’s counsel stated in submissions during the mistrial application, a trial is not a tea party: see also Groia v. Law Society of Upper Canada, 2018 SCC 27,  1 S.C.R. 772, at para. 3. This is particularly the case in criminal proceedings where the stakes are so enormously high for the accused. Defence counsel must feel at liberty to forcefully protect their clients’ interests within the bounds of their professional obligations and the rule of law. A trial judge must intervene with caution so as not to create trial unfairness. At the same time, he or she has a right and an obligation to intervene to control the process, even to intervene to rebuke and correct counsel: Marchand (Litigation guardian of) v. Public General Hospital Society of Chatham, 2000 CanLII 16946 (Ont. C.A.), at para. 154, leave to appeal refused,  S.C.C.A. No. 66; R. v. Ibrahim, 2019 ONCA 631, 147 O.R. (3d) 272, at para. 97.
In R. v. Chambers (Ont CA, 2019) the Court of Appeal held that judicial bias did in fact exist, which is rare. The brief criminal case is useful reading for the facts that an appeal court look to in such cases.
 The appellant raises a number of issues in this appeal. We find it necessary to deal with only the allegations of reasonable apprehension of bias. We see the appellant’s complaints as largely centring upon an appearance of unfairness arising from: (a) the trial judge’s conduct during the trial; and (b) the content of the reasons for judgment. We agree that, when the record is considered as a whole, this case gives rise to an appearance of unfairness that resulted in a miscarriage of justice.R. v. Danial
Here in R v Danial (Ont CA, 2016) the Court of Appeal set out principles that apply to questions to witnesses from the bench:
 During the testimony of the defence witness, the trial judge perceived a lack of clarity as to the conversation that took place between the witness and Samira. At the conclusion of the witness’ testimony, the judge asked a short series of questions in an effort to clarify when those discussions took place. The appellant submits that these questions raised an apprehension of bias on the part of the trial judge.. Laver v. Swrjeski
 We do not accept this submission. There is a presumption of impartiality on the part of the trial judge and a high threshold on the part of an appellant to rebut it.
 A trial judge is entitled to ask questions for clarification. The trial judge here followed the long standing protocol articulated in R. v. Stuckey, 2009 ONCA 151 (CanLII) at para 64. He waited until the conclusion of the witness’ testimony, asked questions for clarification on a narrow issue, and allowed further re-examination. That some of the questions towards the end of the series of questions may have been leading would not lead a reasonable observer being apprised of all the facts to conclude that the trial judge was not impartial.
In Laver v. Swrjeski (Ont CA, 2014) the Court of Appeal also commented on a situation of interventions from the bench in a civil case, here relating to the credibility of police officer witnesses:
 The issue of reasonable apprehension of bias was most recently discussed and considered by this court in Martin v. Sansome, 2014 ONCA 14 (CanLII), 2014 ONCA 14. In that case, the context was interventions by a trial judge during the examination of witnesses. This court set out the legal framework for the assessment of bias in the following passage at paras. 31-33:. R v R.B.
.... In Martin v. Sansome, the appellant was a self-represented litigant. The trial judge tried to help him with procedural issues, but was apparently impatient and frustrated with the slow progress of the trial. On appeal, the court concluded, at para. 39, that, although some of the trial judge’s comments could create the impression of favouring the respondent when viewed in isolation, when the entire record was viewed as a whole, the court was not satisfied that “a reasonable person would have the impression that the trial judge was predisposed to decide the issues before him in favour of the respondent.”
 In Chippewas of Mnjikaning First Nation v. Chiefs of Ontario, 2010 ONCA 47 (CanLII), 2010 ONCA 47, 265 O.A.C. 247, leave to appeal to S.C.C. refused, 33613 (July 18, 2010), at para. 230, this court provided additional guidance:
A determination of whether a trial judge’s interventions give rise to a reasonable apprehension of unfairness is a fact-specific inquiry and must be assessed in relation to the facts and circumstances of a particular trial. The test is an objective one. Thus, the trial record must be assessed in its totality and the interventions complained of must be evaluated cumulatively rather than as isolated occurrences, from the perspective of a reasonable observer throughout the trial.
 In this case, the comments of the application judge did not come in the context of witness testimony but during the oral argument of the application. The application judge made two types of comments that could raise a concern in the mind of a reasonable person that he was predisposed to decide the issues before him in favour of the respondent.
 The first were comments about the credibility of police officers and his concern about making an adverse credibility finding about a police officer. In this case the respondent and his common law wife were officers while the appellant, the mother, was not.
 The second was a number of adverse comments about the credibility of the appellant which were based on misapprehensions of the evidence or the law.
In R v R.B. (Ont CA, 2017) the court comments as follows on the issue of when a judge's interjections at trial result in it being compromised:
 There is a strong presumption that a judge has not unduly intervened in a trial. The question of whether the interventions led to an unfair trial is undertaken from the perspective of a reasonable observer who was present throughout the trial: R. v. Hamilton, 2011 ONCA 399 (CanLII), 271 C.C.C. (3d) 208, at paras. 29-30. Intervening frequently, without more, does not lead to a miscarriage of justice: R. v. Kitaitchik (2002), 2002 CanLII 45000 (ON CA), 166 C.C.C. (3d) 14 (Ont. C.A.). The presence or absence of objections from defence counsel to the judge’s interventions is a relevant factor, although it is not determinative: R. v. Lahouri, 2013 ONSC 2085 (CanLII), 280 C.R.R. (2d) 249 (S.C.), at para. 10.