Gahan v. R., 2014 NBCA 18:
 Relying on Lord Denning’s decision in Jones v. National Coal Board,  2 All E.R. 155,  2 K.B. 55 (C.A.), Mr. Gahan recognizes that a judge can ask questions of a witness to “clear up a point that has been overlooked or left obscure”, but says that, beyond that, if the judge “drops the mantle of the judge and assumes the role of an advocate,” the judge takes on a role that “does not become him well” and risks creating an appearance of partiality (p. 64). He quotes Limerick J.A. in Ogwa v. Alli, 4 N.B.R. (2d) 423,  N.B.J. No. 63 (C.A.) (QL):
A trial judge should not intervene in the examination of witnesses except to clarify the evidence or to establish his jurisdiction. If he does otherwise he runs the risk of becoming an advocate for one party or the other or of becoming involved in a disagreement with the witness under conditions which can remove him from the category of at truly impartial judge. A judge’s function is to listen attentively and not to adduce evidence. [p. 439]
 The facts that prompted Limerick J.A. to make that statement are explained in the two sentences immediately preceding the quoted passage:
During the trial the Court examined seven witnesses. The trial judge asked leading questions of the expert witness Jones and received answers with which he did not agree, and then proceeded to cross-examine the witness at length. [p. 439]
 Notwithstanding this, the appeal in Ogwa was not in the end determined on the basis of the judge’s interference.
 It is an established principle of law that a judge has “not only the right, but also the duty to put questions to a witness in order to clarify an obscure answer or to resolve possible misunderstanding of any question by a witness, even to remedy an omission by counsel, by putting questions which the Judge thinks ought to have been asked in order to bring out or explain relevant matters”: R. v. Darlyn,  B.C.J. No. 94 (C.A.) (QL) per Bird J.A., at para. 31, quoted with approval in R. v. Brouillard, 1985 CanLII 56 (SCC),  1 S.C.R. 39,  S.C.J. No. 3 (QL), at para. 21.
 It is also accepted that the nature and extent of a judge’s participation in the examination of a witness is a matter within the judge’s discretion: ibid.,Boucher v. Doiron, 2000 NBCA 18 (CanLII), 2000 NBCA 18, 230 N.B.R. (2d) 247, at para. 17, and Pelletier v. St.-Onge, 2001 NBCA 22 (CanLII), 2001 NBCA 22, 236 N.B.R. (2d) 128, at para. 9, both per Drapeau J.A. (as he then was). Evidently, the discretion must be exercised judicially as part of the judge’s function to “keep the scales of justice in even balance between the Crown and the accused”: Darlyn, at para. 31, and Brouillard, at para. 21.
 Of course, if a judge, figuratively speaking, steps down from the bench and assumes the role of counsel to the point that a reasonable person would consider that the accused has not had a fair trial, a new trial will have to be ordered even if the verdict is not unreasonable having regard to the evidence and even if the judge has not erred with respect to the law and the facts: Brouillard, R. v. Palosaari, 2004 BCCA 595 (CanLII), 2004 BCCA 595,  B.C.J. No. 2429 (QL), and R. v. Konelski,  A.J. No. 615 (C.A.) (QL). The appearance of fairness is of as fundamental importance as fairness itself.