Does the erroneous jury instruction require reversal of the armed bank robbery conviction?

Because the erroneous jury instruction requires reversal of the armed bank robbery conviction, our inquiry regarding that charge concerns only whether the evidence supporting the conviction is sufficient to allow the government to retry the armed robbery charge on remand. See Burks v. United States, 437 U.S. 1, 11, 98 S.Ct. 2141, 2147, 57 L.Ed.2d 1 (1978) (defendant cannot be retried when reviewing court has determined that the evidence was insufficient to sustain the jury's verdict). We conclude that the evidence was insufficient to sustain a conviction and that retrial is therefore prohibited.