R. v. Aragon, 2022 ONCA 244, March 24, 2022, at paragraphs 37 to 40:
As a general rule, trial judges have discretion to determine the form that an admissibility voir dire will take, based on the issues involved and the nature of the case being tried…In many cases it is therefore not only common, but preferable in the interests of efficiency, to conduct admissibility voir dires based on information that would not be admissible during the trial proper: Evans, at paras. 116, 147-48 (statements of counsel and filed documents); Dietrich, at paras. 43-50 (endorsing the use of summaries of the evidence); R. v. Snow (2004), 190 C.C.C. (3d) 317 (Ont. C.A.), at paras. 60-61, (preliminary inquiry records); R. v. G.N.D. (1993), 81 C.C.C. (3d) 65 (Ont. C.A.), at paras. 30, 38 (summary of proposed hearsay statement and cross-examination of witnesses to the statement).
This is not to say there are never cases where admissible evidence will be required to establish contested facts in an admissibility voir dire. There are passages, for example, supporting the proposition that oral evidence must be presented in contested voluntariness voir dires (Dietrich, at para. 44; Snow, at para. 61) and in contested Charter admissibility voir dires (R. v. Tomlinson, 2009 BCCA 196, 190 C.R.R. (2d) 28, at para. 51). Whether or not oral testimony is always required in voluntariness and Charter admissibility voir dires where the underlying facts are contested, this is not the case in extrinsic discreditable conduct admissibility voir dires. In Snow, a ground of appeal based on the refusal of the trial judge to require oral evidence in an extrinsic discreditable conduct admissibility voir dire was denied by this court as being without merit.
I am nonetheless persuaded that in exercising discretion relating to the manner in which any admissibility voir dire is conducted, trial judges should take a functional approach to ensure that the record before them enables factual determinations required to determine admissibility to be fairly made, and they should disregard contested information that has been received that cannot fairly be assessed where it is important to do so. For example, in Snow the decision of the trial judge to resolve the admissibility of extrinsic conduct evidence based on transcripts of related guilty pleas and preliminary inquiry transcripts was supported by the fact that in that case, the “admissibility of the similar fact evidence did not require the testing of circumstances surrounding the evidence, nor was there uncertainty about what the witnesses might say”: Snow, at para. 61.
No doubt because of the functional needs in an extrinsic discreditable conduct evidence admissibility voir dire,it is typical that contested“evidence of other discreditable conduct is introduced through the testimony of those who suffered it (if alive), observed it, or, as admissible hearsay, by those to whom the victim reported it”: R. v. Stubbs, 2013 ONCA 514, 300 C.C.C. (3d) 181, at para. 68. The formal presentation of admissible evidence is optimal where material facts relating to admissibility are contested because the strength of the evidence establishing that the alleged discreditable conduct even occurred is an important consideration in evaluating the probative value of the proposed extrinsic discreditable conduct evidence: R. v. Mahalingan, 2008 SCC 63,  3 S.C.R. 316, at para. 163. If, on a threshold examination, the evidence alleging the extrinsic discreditable conduct is of questionable credibility or reliability, the probative value of the proposed discreditable conduct evidence will be diminished: Handy, at paras. 133-36; R. v. MacCormack, 2009 ONCA 72, 241 C.C.C. (3d) 516, at para. 54. Indeed, unless the proposed discreditable conduct evidence is reasonably capable of belief, it may be too prejudicial to admit: Handy, at para. 134.