What is the primary purpose for obtaining a warrant for surveillance without a warrant?

Defendants rely on the primary purpose test articulated in United States v. Truong Dinh Hung, 629 F.2d 908 (4th Cir.1980). Truong held that the foreign intelligence exception to the warrant requirement applies "only when the surveillance is conducted 'primarily' for foreign intelligence reasons." Id. at 915. One other court has applied the primary purpose test. United States v. Duggan, 743 F.2d 59, 77 (2d Cir.1984). Another court has rejected it. United States v. Falvey, 540 F.Supp. 1306, 1313-14 (E.D.N.Y.1982) (distinguishing Truong ). A third court has declined to decide the issue. Matter of Kevork, 634 F.Supp. 1002, 1015 (C.D.Cal.1985), aff'd, 788 F.2d 566 (9th Cir.1986).