Can an appellate court substitute its own findings of credibility for that of the trial judge?

An appellate court ought not to substitute its own views for that of the trial judge once it finds a reasonable evidentiary foundation existed. With respect to findings of credibility, an appellate court is not permitted to substitute its own conclusion in regards to a witness that the court has neither seen nor heard. Where a conviction turns on the question of credibility, an appellate court may only overturn the conviction if it is satisfied that the basis for finding of credibility is so tenuous, fraught with difficulties or the evidence incredible to the extent that the trial judge’s credibility assessment cannot be said to have been supported by the evidence. Francois v. The Queen (1994), 1994 CanLII 52 (SCC), 91 C.C.C. (3d) 289 (S.C.C.).