What is the test for self-serving statements in a criminal case?

In my opinion, the matter is governed by the following passage from the judgment of Ritchie J. in Regina v. Graham, 1972 CanLII 172 (SCC), [1972] 4 W.W.R. 488 at 494, 19 C.R.N.S. 117, 7 C.C.C. (2d) 93, 26 D.L.R. (3d) 579 (Can): "… the general rule in criminal cases [is] that self-serving statements made by an accused cannot be introduced on the cross-examination of third parties because they cannot themselves be tested by cross-examination of the accused person who made them, and their introduction in such manner deprives the jury of the benefit of appraising his credibility from observing his demeanour."