While an appellate court may hear and decide new issues not raised at trial, its discretion to do so should not be exercised routinely or lightly.
R. v. Guindon, 2015 SCC 41 (CanLII), 3 S.C.R 3, at para. 22.
Before doing so, the court must be satisfied that the new issue raised on appeal can be fully, effectively and fairly addressed even though it was not raised at trial.
R. v. K.R., 2009 ONCA 156 (CanLII), 246 O.A.C. 96, at para. 7.
It is not appropriate for an appellate court to exercise its jurisdiction and decide a controversial issue in the midst of an evidentiary vacuum. And where the Appellant and the Respondent take the same position on the newly-raised issue, the court does not have the benefit of having the issue advanced within the usual adversarial paradigm.
See for instance R. v. Dhanaswar, 2016 ONCA 229 (CanLII).