Legal Question in Criminal Law in Canada

You mean if the person testified already in a court proceeding and therefore a transcript is available? You are not referring to a witness now deceased who provided an affidavit that wasn't subject to cross-examination.

See Criminal Code provision 715

https://laws-lois.justice.gc.ca/eng/acts/c-46/page-181.html#h-130564

715 (1) Where, at the trial of an accused, a person whose evidence was given at a previous trial on the same charge, or whose evidence was taken in the investigation of the charge against the accused or on the preliminary inquiry into the charge, refuses to be sworn or to give evidence, or if facts are proved on oath from which it can be inferred reasonably that the person

(a) is dead,

(b) has since become and is insane,

(c) is so ill that he is unable to travel or testify, or

(d) is absent from Canada,

and where it is proved that the evidence was taken in the presence of the accused, it may be admitted as evidence in the proceedings without further proof, unless the accused proves that the accused did not have full opportunity to cross-examine the witness.

Admission of evidence

(2) Evidence that has been taken on the preliminary inquiry or other investigation of a charge against an accused may be admitted as evidence in the prosecution of the accused for any other offence on the same proof and in the same manner in all respects, as it might, according to law, be admitted as evidence in the prosecution of the offence with which the accused was charged when the evidence was taken.

Admission of evidence

(2.1) Despite subsections (1) and (2), evidence that has been taken at a preliminary inquiry in the absence of the accused may be admitted as evidence for the purposes referred to in those subsections if the accused was absent further to the permission of a justice granted under paragraph 537(1)(j.1).

Absconding accused deemed present

(3) For the purposes of this section, where evidence was taken at a previous trial or preliminary hearing or other proceeding in respect of an accused in the absence of the accused, who was absent by reason of having absconded, the accused is deemed to have been present during the taking of the evidence and to have had full opportunity to cross-examine the witness.

Exception

(4) Subsections (1) to (3) do not apply in respect of evidence received under subsection 540(7).