Is the application of a legal test to specific facts a legal or mixed question of fact and law?

R. v. Hirsekorn, 2012 ABCA 21 deals with whether the application of a legal test to specific facts can give rise to an error of law. The Court holds it can -- an important point for appeal purposes:

[14] I do not agree with the respondent that the second question is one of mixed law and fact. The misapplication of a legal test can raise a question of law, see Canada (Director of Investigation and Research) v Southam Inc, 1997 CanLII 385 (SCC), [1997] 1 SCR 748, 144 DLR (4th) 1 at paras 35 and 39; and Housen v Nikolaisen, 2002 SCC 33 (CanLII), 2002 SCC 33 at para 36, 2002 SCC 33 (CanLII), [2002] 2 SCR 235. Part of the applicant's argument about the misapplication of Powley concerns the summary conviction appeal judge's failure (at para 122) to identify the historic rights-bearing community (the second part of the Powley test). Without such an identification, asserts the applicant, the balance of the test cannot be properly applied. This is a legal argument extricable from the trial judge's fact findings and, based on Southam and Housen, a question of law.