What is the test for granting a foreign request for international legal assistance?

The basic principle is set out in the oft-quoted words of Dickson J. (as he then was) speaking for the court in R. v. Zingre, 1981 CanLII 32 (SCC), [1981] 2 S.C.R. 392 at p. 401: It is upon this comity of nations that international legal assistance rests. Thus the courts of one jurisdiction will give effect to the laws and judicial decisions of another jurisdiction, not as a matter of obligation but out of mutual deference and respect. A foreign request is given full force and effect unless it be contrary to the public policy of the jurisdiction to which the request is directed (see Gulf Oil Corporation v. Gulf Canada Ltd. et al., 1980 CanLII 192 (SCC), [1980] 2 S.C.R. 39) or otherwise prejudicial to the sovereignty or the citizens of the latter jurisdiction.