What is the effect of a district court's observation of a juror's demeanor at a voir dire?

Hernandez, 500 U.S. at 365, 111 S.Ct. at 1869 (quoting Wainwright v. Witt, 469 U.S. 412, 428, 105 S.Ct. 844, 854, 83 L.Ed.2d 841 (1985)). Here, the district court's observation of demeanor was particularly important, since the court had to assess not only the credibility of the attorneys, but also the credibility of those jurors who purported to have been reformed through the educative process of the voir dire. The two credibility assessments were interrelated: the more convincing the juror, the less believable the attorney who attempted to exercise the challenge.