What is the test for proving possession of a controlled substance?

We review the sufficiency of the evidence in the light most favorable to the prosecution in order to determine whether "any reasonable trier of fact could have found the essential elements of the crime beyond a reasonable doubt." United States v. Kuball, No. 92-30063, slip op. 11731, 11735 (9th Cir. Sept. 30, 1992). Possession of a controlled substance may be actual or constructive. United States v. Restrepo, 930 F.2d 705, 709 (9th Cir.1991). In order to show possession, the government must prove that the defendant had dominion and control over the contraband. Id.