Evidence - Witness Demeanour'Witness demeanour' means a witness' demeanour while giving testimony. 'Demeanour evidence' (a separate topic) means a witness' observations of the emotional state of a person that they are testifying about.
. R. v. Brown
In R. v. Brown (Ont CA, 2022) the Court of Appeal comments on demeanour evidence, here the demeanour of a witness during a 911 call recording:
 ... The trial judge was, however, entitled to use the complainant’s demeanour on the 911 call to draw inferences about the credibility of the complainant’s account, and to rely on this evidence as supporting her testimony of having experienced a violent sexual assault: R. v. Khan, 2017 ONCA 114, 136 O.R. (3d) 520, leave to appeal refused,  S.C.C.A. No. 139, at paras. 31-34; R. v. Steele, 2021 ONCA 186, at para. 94. .... R. v. Panchal
In R. v. Panchal (Ont CA, 2022) the Court of Appeal considered the demeanour of a witness towards the credibility of their evidence:
(d) Demeanor evidence. R. v. J.L.
 I also do not accept that the trial judge over-relied on the demeanour of Mr. Solanki in assessing his credibility. As this court has recently stated, “[t]he starting point is that although its admission may be somewhat rare, there is no bar to the admission of demeanour evidence”: R. v. Staples, 2022 ONCA 266, at para. 38. It is settled law that demeanour evidence is a factor that a trial judge is entitled to consider, provided it is not the exclusive determinant of his or her credibility assessment. As stated by this court in R. v. A.A., 2015 ONCA 558, 327 C.C.C. (3d) 377, at paras. 131-32:
 It is beyond dispute that demeanour is a factor the trier of fact is entitled to consider in assessing the credibility of witnesses and the reliability of their testimony.
 On the other hand, it is equally well settled that a witness’s demeanour cannot become the exclusive determinant of his or her credibility or of the reliability of his or her evidence. [Citations omitted.]
In R. v. J.L. (Ont CA, 2022) the Court of Appeal considered witness demeanour during testimony:
 It is appropriate for trial judges to consider the demeanour of witnesses when evaluating their credibility: R. v. R.D., 2016 ONCA 574, 352 O.A.C. 350, at para 25; R. v. E.A.P., 2022 ONCA 134, at para. 21. However, this court has cautioned that demeanour can be an unreliable gauge of credibility because of the impact that culture, personality and pressure can have on courtroom behaviour, and the risk that stereotypes about credibility will distort the evaluation: R. v. Rhayel, 2015 ONCA 377, 334 O.A.C. 181, at para. 85; R. v. Santhosh, 2016 ONCA 731, 342 C.C.C. (3d) 41; R. v. Hemsworth, 2016 ONCA 85, 334 C.C.C. (3d) 534; R. v. A.A., 2015 ONCA 558, 327 C.C.C. (3d) 377, at paras. 131-32; R. v. T.M., 2014 ONCA 854, 318 C.C.C. (3d) 421. Therefore, it is an error to give undue weight to demeanour in making credibility determinations. Although the trial judge arguably gave more attention to demeanour in his reasons for judgment than is optimal, we are left unpersuaded that the trial judge erred by giving undue weight to demeanour.. R v Rhayel
In R. v. Rhayel (Ont CA, 2015) the Court of Appeal cautioned against undue reliance by the trier of fact on a witness' demeanour during testimony, as follows:
 Cases in which demeanour evidence has been relied upon reflect a growing understanding of the fallibility of evaluating credibility based on the demeanour of witnesses: see Law Society of Upper Canada v. Neinstein (2010), 2010 ONCA 193 (CanLII), 99 O.R. (3d) 1 (C.A.), at para. 66; R. v. G. (P.), 2012 ONSC 4646 (CanLII), 104 W.C.B. (2d) 390, at paras. 31-33; 9129-9321 Quebec Inc. v. R., 2007 TCC 2 (CanLII),  T.C.J. No. 23, at para. 31; R. v. Powell,  O.J. No. 555, at paras. 9-10. It is now acknowledged that demeanour is of limited value because it can be affected by many factors including the culture of the witness, stereotypical attitudes, and the artificiality of and pressures associated with a courtroom. One of the dangers is that sincerity can be and often is misinterpreted as indicating truthfulness.. R v E.H.
 In R. v. G.(M.) (1994), 1994 CanLII 8733 (ON CA), 93 C.C.C. (3d) 347 (C.A.), at p. 355, this court quoted with approval the following passage from Faryna v. Chorny,  2 D.L.R. 354 (B.C.C.A.), at pp. 356-57:
If a trial judge's finding of credibility is to depend solely on which person he thinks made the better appearance of sincerity in the witness box, we are left with a purely arbitrary finding and justice would then depend upon the best actors in the witness box. On reflection it becomes almost axiomatic that the appearance of telling the truth is but one of the elements that enter into the credibility of the evidence of a witness. This cautious approach to demeanour was echoed by the Alberta Court of Appeal in R. v. Pelletier (1995), 1995 ABCA 128 (CanLII), 165 A.R. 138, at para. 18, citing a 1973 paper by Justice MacKenna:
For a trial judge to say "I believe him because I judge him to be telling the truth," is to come to a conclusion on consideration of only half the problem. In truth it may easily be self-direction of a dangerous kind.
I question whether the respect given to our findings of fact based on the demeanour of the witnesses is always deserved. I doubt my own ability, and sometimes that of other judges, to discern from a witness’s demeanour, or the tone of his voice, whether he is telling the truth. He speaks hesitantly. Is it the mark of a cautious man, whose statements are for that reason to be respected, or is he taking time to fabricate? Is the emphatic witness putting on an act to deceive me, or is he speaking from the fullness of his heart, knowing that he is right? Is he likely to be more truthful if he looks me straight in the face than if he casts his eyes on the ground, perhaps from shyness or a natural timidity? For my part I rely on these considerations as little as I can help. A powerfully-worded and thoroughly-researched analysis of reliance on demeanour evidence can be found in the decision of the High Court of Australia in State Rail Authority of New South Wales v. Earthline Constructions Pty. Ltd. (1999), 160 A.L.R. 588. At para. 88, the Court says:
There is growing understanding, both by trial judges and appellate courts, of the fallibility of judicial evaluation of credibility from the appearance and demeanour of witnesses in the somewhat artificial and sometimes stressful circumstances of the courtroom. Scepticism about the supposed judicial capacity in deciding credibility from the appearance and demeanour of a witness is not new. In Societe D’Avances Commerciales (Societe Anonyme Egyptienne) v Merchants’ Marine Insurance Co (The “Palitana”), Atkin LJ remarked that “an ounce of intrinsic merit or demerit in the evidence, that is to say, the value of the comparison of evidence with known facts, is worth pounds of demeanour.” To some extent, the faith in the judicial power to discern credibility from appearance was probably, at first, a consideration which the judiciary assumed that it inherited from juries. It was natural enough that trial judges, accustomed to presiding over jury trials, would claim, and appellate judges would accord, the same “infallible” capacity to tell truth from falsehood as had historically been attributed to the jury. Nowadays, most judges are aware of the scientific studies which cast doubt on the correctness of this assumption. I agree with the suggestion contained at the conclusion of the Court’s analysis in the State Rail Authority decision that it is important for trial judges to bear in mind that, to the extent possible, they should try to decide cases that require assessing credibility without undue reliance on such fallible considerations as demeanour evidence.
In R v E.H. (Ont CA, 2020) the Court of Appeal considers the treatment of witness demeanour:
 Triers of fact, whether judges or jurors, must guard against undue reliance on demeanour. That does not mean that demeanour is irrelevant. It is one of the factors that a trial judge may consider in evaluating a witness’s credibility: R. v. O.M., 2014 ONCA 503, 313 C.C.C. (3d) 5, at para. 34; R. v. T.H., 2016 ONCA 439, at para. 4. In this case, demeanour was just one of the factors that the trial judge relied upon in making his credibility assessments. He did not over-emphasize demeanour, nor did he treat it as a controlling factor.. R. v. Chacon-Perez
In (Ont CA, 2021) the Court of Appeal (Watt JA) considers the fallibility of witness demeanour as an indicator of credibility:
Demeanour Evidence. R. v. G.M.C.
 Testimonial demeanour is a relevant consideration in evaluating the credibility of any witness, including an accused: R. v. M.(O.), 2014 ONCA 503, 313 C.C.C. (3d) 5, at para. 34. But as a predictor of testimonial accuracy, a witness’ demeanour is fallible. Its fallibility is a function of many and disparate factors. The culture of the witness. Stereotypical attitudes. The artificiality of and pressures associated with a courtroom: Law Society of Upper Canada v. Neinstein, 2010 ONCA 193, 99 O.R. (3d) 1, at para. 66; R. v. Hemsworth, 2016 ONCA 85, 334 C.C.C. (3d) 534, at para. 44.
 The fallibility of a witness’ demeanour as a measuring stick of testimonial accuracy signals caution in its role. It is but one of many factors. Not exclusive. And not predominant: Hemsworth, at para. 45.
In R. v. G.M.C. (Ont CA, 2021) the Court of Appeal considered 'witness demeanour', that is the assessment of credibility by the demeanour of the witness (eg. antagonism):
 As we observed in R. v. Hemsworth, 2016 ONCA 85, 334 C.C.C. (3d) 534, at paras. 44-45, reliance on demeanour must be approached cautiously and it is of limited value in the assessment of credibility:
This court has repeatedly cautioned against giving undue weight to demeanour evidence because of its fallibility as a predictor of the accuracy of a witness's testimony: Law Society of Upper Canada v. Neinstein, 2010 ONCA 193, 99 O.R. (3d) 1, at para. 66; R. v. Rhayel, 2015 ONCA 377, 324 C.C.C. (3d) 362. As I indicated in Rhayel, at para. 85, "[i]t is now acknowledged that demeanour is of limited value because it can be affected by many factors including the culture of the witness, stereotypical attitudes, and the artificiality of and pressures associated with a courtroom."
Although the law is well settled that a trial judge is entitled to consider demeanour in assessing the credibility of witnesses, reliance on demeanour must be approached cautiously: see R. v. S. (N.), 2012 SCC 72,  3 S.C.R. 726, at paras. 18 and 26. Of significance in this case is the further principle that a witness's demeanour cannot become the exclusive determinant of his or her credibility or of the reliability of his or her evidence: R. v. A. (A.), 2015 ONCA 558, 327 C.C.C. (3d) 377, at para. 131; R. v. Norman (1993), 1993 CanLII 3387 (ON CA), 16 O.R. (3d) 295 (C.A.), at pp. 313-14.