support a “defendant’s argument that the witness is not credible ... so long as the comment does not constitute an assurance by the prosecutor that the witness is credible.” Id. In other words, a “prosecutor may argue in the negative that the assertions made by defense counsel that a witness is lying are not supported by the testimony in the record.” Id. Since our decision in Walker, we have had several opportunities to revisit the vouching issue. In almost every instance, we have held that the district court did not err in denying a mistrial. See United States v. Milan, 304 F.3d 273, 289-90 (3d Cir.2002); United States v. Nelson, 284 F.3d 472, 476 n. 3 (3d Cir.2002); United States v. Saada, 212 F.3d 210, 225 (3d Cir.2000); United States v. Helbling, 209 F.3d 226, 240-41 (3d Cir.2000) (<HOLDING>); cf. Lam v. Kelchner, 304 F.3d 256, 271-72 (3d
holding that the trial courts error in not allowing defendant to testify on direct examination as to nature and circumstances of prior convictions was not harmless error where credibility of the defendant was critical to the deliberations of the jury holding that any error was harmless and thus not plain error holding that the defendant did not show prejudice to support ineffective assistance of counsel because any evidentiary error was harmless holding that any vouching by prosecutor was harmless error because the judge informed the jury not to consider the relevant comments there was a great deal of evidence to support the conviction and defendant was not prejudiced holding that the fact that a judge had ruled against the defendant is not a basis for finding the judge prejudiced