What is the test for challenging a jury's instructions in a criminal case?

"[A]lthough a criminal defendant is entitled to an instruction regarding his theory of the case, challenges which merely pertain to the trial judge's language or formulation of the charge are reversible only for an abuse of discretion." United States v. Cruz, 783 F.2d 1470, 1472 (9th Cir.1986) (quoting United States v. Marabelles, 724 F.2d 1374, 1382-83 (9th Cir.1984)). The trial judge is given substantial latitude in tailoring the instructions so long as they fairly and adequately cover the issues presented. Id. Also, when reviewing a claim of error relating to jury instructions, the instructions must be viewed as a whole. Id.