What is the test for appeal judges to grant leave to allow a party to argue an entirely new issue on appeal?

The rationale for the general rule that appellate courts will not entertain an entirely new issue on appeal is that “it is unfair to spring a new argument upon a party at the hearing of an appeal in circumstances in which evidence might have been led at trial if it had been known that the matter would be an issue on appeal”. The party seeking to raise the new argument must persuade the appellate court that the facts necessary to address the point are before the court “as fully as if the issue had been raised at trial”, a burden more easily met if the issue is one of law. The decision whether to grant leave to allow a new argument is discretionary, “guided by the balancing of the interests of justice as they affect all parties”: Kaiman v. Graham, 2009 ONCA 77, 245 O.A.C. 130, at para. 18.