What is the standard of review of a learned trial judge’s decision?

First, we must comment on the standard of review by this appeal court of the learned trial judge’s decision. An appeal is not a retrial of a case. The standard of review on pure questions of law is one of correctness, and an appellate court is thus free to replace the opinion of the trial judge with its own. The standard of review for findings of fact is such that they cannot be reversed unless the trial judge has made a "palpable and overriding error". A palpable error is one that is plainly seen. Questions of mixed fact and law involve the application of a legal standard to a set of facts, that is, it is subject to a standard of palpable and overriding error, unless it is clear that the trial judge made some extricable error in principle with respect to the characterization of the standard or its application, in which case the error may amount to an error of law, subject to a standard of correctness. [Housen v. Nikolaisen [2002] 2 S.C.R. 235, 2002 SCC 33].