What is the test for sustaining a conviction for importation and possession of a controlled substance?

"We will uphold a conviction if, viewing the evidence in the light most favorable to the government, any rational trier of fact could have found the defendant guilty beyond a reasonable doubt of each element of the crime charged." United States v. Sanchez-Mata, 925 F.2d 1166, 1166 (9th Cir.1991). In order to sustain a conviction for importation and possession of a controlled substance, the government must establish that the defendant knew of the contraband and had the power to exercise dominion and control over it. See id. at 1169; 21 U.S.C. 952, 960. Morales maintains that the evidence was insufficient to show that he knew of or possessed the contraband.