Credibility refers to the trustworthiness of a witness. Credibility evidence comprises evidence admitted for the purposes of strengthening or weakening the testimony of a witness or an accused. Credibility evidence that is used to impeach a witness can be submitted at any point from the time the witness takes the stand. The rule is that a witness always puts their credibility at issue whenever they testify and so it is open to attack. Evidence that bolsters a witness's credibility, however, is not admittable until the credibility of that witness has been impeached.
Whenever testimony is given the trier of fact must determine whether the testimony is to be believed. There is no presumption of honesty among witnesses in a criminal trial
There are several approaches to determining credibility. One school of thought believes that credibility is determined primarily by demeanour and conduct in trial. Another approach says that demeanour and conduct are too subjective, and so the best approach is to consider the consistency of testimony when compared to reliable facts.
A related point of review is where the judge makes an error of law by applying a "stricter standard of scrutiny than the evidence of the Crown" as it relates to evaluating credibility.However, this route of appeal is not be to be used as a "veiled invitation to reassess the trial judge’s credibility determinations."
Raymond v Bosanquet, 1919 CanLII 11, (1919) 59 SCR 452 at p.460
see discussion on credibility and reliability in R v C. (H.), 2009 ONCA 56 (CanLII) at para 41
- R v Thain 2009 ONCA 223 (CanLII), (2009), 243 CCC (3d) 230 (Ont. C.A.), at para 32.
Raymond v Bosanquet, supra
R v White, 1947 CanLII 1 (SCC),  SCR 268 at 272
Tatarchuk v Sidor (1951), 1 W.W.R. (N.S.) 435 at 448 (Alta. C.A.)(*no CanLII links)
R v P. (R.) 1994 CanLII 6250, (1994), 94 CCC (3d) 571 (Que. C.A.)
R v Norman 1993 CanLII 3387, (1993), 16 O.R. (3d) 295 (C.A.)
R v Marzan (1982), 18 Man. R. (2d) 240(*no CanLII links) at 246
R v Neary, 2000 NFCA 22 (CanLII) at para 27
R v Oldford, 2001 NFCA 34 (CanLII) at para 75
Faryna v Chorny  2 D.L.R. 354 (BCCA)(*no CanLII links)
- In short, the real test of the truth of the story of a witness in such a case must be its harmony with the preponderance of the probabilities which a practical and informed person would readily recognize as reasonable in that place and in those conditions.
R. v Aird, 2013 ONCA 447 (CanLII) at para 39
R. v Marshall, 2015 ONCA 692 (CanLII)
- R. v Howe (sub nom J.H.) 2005 CanLII 253 (ON CA),  O.J. No. 39 (C.A.) at para 46
R v RL, 2016 ONCA 455 (CanLII) at para 46
Howe, supra per Doherty J.A
R v TT, 2009 ONCA 613 (CanLII), at paras 28 and 31
- Aird, supra, at para 39
It is generally prohibited to adduce any evidence for the sole purpose of bolstering or increasing a witnesses credibility, suggesting they are more likely to be telling truth. Evidence that is adduced for another reason and also has the effect of bolstering credibility can be permitted. The judge must balance the probative value of the evidence against the prejudicial effect. Reasons for adducing oath-helping evidence includes showing corroboration with other extrinsic evidence and narrative.
The Crown cannot introduce evidence showing that their witness has testified in court previously resulting in convictions.
The Defence cannot adduce evidence establishing that the accused passed a polygraph test.
Failure to Call Witnesses
In certain circumstances, adverse inferences may be made from a party's failure to call a witness. Any inference should be made from "ordinary logic and experience" and only where there is "plausible reason for nonproduction".
There are many circumstances where there is reason not to call a witness that is unrelated to honesty, such as due to overlap with other witnesses, poor demeanor, or limited relevancy. However, a negative inference is more likely drawn where the witness is able to provide "missing proof" that would be important to the case.
R v Lapensee, 2009 ONCA 646 (CanLII) at para 41 per O'Connor ACJO
R v Jolivet,  1 SCR 751, 2000 SCC 29 (CanLII), at para 25 per Binnie J
- Lapensee, supra
- Lapensee, supra
- Lapensee, supra
- R v Ruiz 1991 CanLII 2410 (NB CA), (1991), 68 CCC (3d) 500 (N.B.C.A.), at p. 505 per Angers J.A. (dissenting, but not on this point), aff’d on other grounds 1993 CanLII 84 (SCC),  3 SCR 649 per La Forest J
R v Charette, (1982), 67 CCC (2d) 357 (Ont. C.A.)(*no CanLII links)
at p. 359
See also R v Zehr, (1980), 54 CCC (2d) 65 (Ont. C.A.) (*no CanLII links) at p. 68
R v Koffman and Hirschler, (1985), 20 CCC (3d) 232 (Ont. C.A.)(*no CanLII links) , at p. 237
R v Dupuis 1995 CanLII 1543 (ON CA), (1995), 98 CCC (3d) 496 (Ont. C.A.), at p. 508 per Osborne JA
R v Witter 1996 CanLII 4005 (ON CA), (1996), 105 CCC (3d) 44 (Ont. C.A.), at p. 55 per Doherty JA
R v Marshall 2005 CanLII 30051 (ON CA), (2005), 77 O.R. (3d) 81 (C.A.), at para 47 per Borins JA
Accused's Failure to Testify
- Collateral Fact Rule
- Bias, Interest, and Corruption
- Prior Consistent Statements
- Prior Inconsistent Statements
- Adverse and Hostile Witnesses
- Post-Offence Conduct
- Criminal Record
- Complainant's Sexual History
- Disreputable and Unsavoury Witnesses
- Analyzing Testimony