How has the court interpreted reasonable doubt in a jury trial?

Prior panels of this court have stressed that "instructions tying 'reasonable doubt' to a doubt 'for which you can give a reason' ... may well be unwise, because of the possibility that such an instruction will 'intimidate a juror by suggesting that he may be called upon to explain his doubts.'" Vargas, 86 F.3d at 1277 (quoting United States v. Davis, 328 F.2d 864, 867 (2d Cir. 1964)). In Vargas we upheld a reasonable doubt instruction of this variety based on two countervailing considerations. First, we found that the surrounding passages in the instruction directed the jury to ground their decisions in the evidence, such that the "reason" a juror would think herself expected to give would simply be a reason based in the evidence, and not one exceeding degree of doubt required for acquittal. See id. at 1278 ("[T]he jury was unlikely to have understood the challenged language to bear upon the degree or quantum of doubt necessary for acquittal, but rather, upon the appropriate basis for the formulation of a doubt sufficient for acquittal."). Second, we reasoned that the surrounding passages sufficiently emphasized the prosecution's burden of proof, such that the jurors were unlikely to understand the instruction as demanding that they look to each other or to the defendant to supply a reason to acquit. See id. at 1278-79.