The default position for a judge at a criminal trial in Canada is that hearsay evidence is inadmissible. As a general rule, a party is not permitted to have an out of court statement repeated in court for the truth of its contents, having regard to opposing counsel’s difficulty in testing the evidence in the presence of the judge or jury (e.g. R. v. Khalewon, 2006 SCC 57 at para. 34).
That being said, the common law recognizes that sometimes the admission of sufficiently reliable hearsay is necessary for the proper adjudication of an allegation of criminal misconduct. As Karakatsanis, J., speaking for a majority of the Supreme Court of Canada, states in R. v. Bradshaw,  S.C.J. No. 35, beginning at para. 23:
... Under the principled exception, hearsay can exceptionally be admitted into evidence when the party tendering it demonstrates that the twin criteria of necessity and threshold reliability are met on a balance of probabilities (Khelawon, at para. 47).
By only admitting necessary and sufficiently reliable hearsay, the trial judge acts as an evidentiary gatekeeper. She protects trial fairness and the integrity of the truth-seeking process (Youvarajah, at paras. 23 and 25)...
- "...Even when the trial judge is satisfied that the hearsay is necessary and sufficiently reliable, she has discretion to exclude this evidence if its prejudicial effect outweighs its probative value. ...." (Bradshaw, at para. 24).