What is the burden of proving a defendant's innocence?

In challenging the sufficiency of the evidence to support his conviction, a defendant bears a heavy burden. In order to prevail, he must show that, after viewing the evidence in the light most favorable to the government, a rational jury could not have found him guilty beyond a reasonable doubt. See, e.g., United States v. Matthews, 20 F.3d 538, 548 (2d Cir.1994). The government "need not exclude 'every possible hypothesis of innocence.' " United States v. Sureff, 15 F.3d 225, 228 (2d Cir.1994) (quoting United States v. Friedman, 998 F.2d 53, 59 (2d Cir.1993)).