R. v. Tash, 2013 ONCA 380 holds:
 Credibility rules are of three types.
 The first type concerns attempts by the witness' proponent to bolster the witness' credibility even before it has been impeached. As a general rule, we do not permit the witness' proponent to elicit bolstering evidence in direct examination. The rule against "oath-helping" excludes it.
 The second group of credibility rules involves the techniques an opponent may invoke to attack or impeach a witness' credibility.
 The third set of rules governs the method that the witness' proponent may use to rehabilitate the witness' credibility after impeachment, in essence, to undo the damage done by the impeachment.
 Despite the hostility of the common law towards bolstering evidence, we liberally admit impeaching evidence. Among the modes of attack on a witness' credibility are attacks that show bias or corruption, and those that attack the witness' character. A witness may also be impeached by specific contradiction, in other words, by proof through other witnesses that material facts are otherwise than as described by the witness being impeached.
 We recognize that a witness' emotions or feelings towards the parties, or the witness' self-interest in the outcome of the case, may have a powerful distorting effect on human testimony. And so it is that we recognize that bias, or any conduct, relationships, or motives reasonably likely to produce it, may be established to impeach credibility. The disparate and varied kinds of sources of partiality defy exhaustive listing, but doubtless include hostility or attitude towards an accused.
 A witness' character for truthfulness or mendacity is relevant circumstantial evidence on the question of the truthfulness of the witness' testimony. Evidence of a witness' previous deception tends to demonstrate a character for untruthfulness. In turn, the existence of such a character trait increases, at least slightly, the probability that the witness has lied under oath. Proof of a witness' character trait for untruthfulness can be accomplished in several ways including proof of prior untruthful conduct, the witness' associations, and prior history. Any other acts offered to establish character should have a significant relation to credibility.
 Our adversary system requires that the proponent of a witness be afforded an opportunity to meet attacks on the credibility of the witness by presenting evidence rehabilitating the witness. But the bolstering evidence must be responsive to the nature of the attack and not exceed permissible limits. For example, supportive evidence of good character for honesty of a witness impeached by evidence of "bad" character for untruthfulness or dishonesty is permissible. Proof of prior consistent statements to rebut impeachment on grounds of recent fabrication is also permissible. At root, the admissibility of rehabilitative evidence should depend on whether what is proposed is logically relevant to rebut the impeaching fact. The rehabilitating facts should meet the impeachment with relative directness. The wall, attacked at one point, may not be fortified at a distinctly separate point: 1 McCormick on Evidence (7th ed., 2013, Thomson Reuters: Westlaw), at § 47, pp. 307-308.