Does a prosecutor's statement that the credibility of government witnesses was supported by a lack of evidence presented by the defense was not improper?

The prosecutor's statement that the credibility of the government witnesses was supported by a lack of evidence presented by the defense was likewise not improper. Improper vouching occurs where the prosecutor indicates that the government is aware of information which further proves the defendant's guilt and is outside the jurors' knowledge. See United States v. Roberts, 618 F.2d 530, 533-34 (9th Cir.1980). Arguing inferences from a lack of evidence does not imply that the government has additional knowledge apart from what was presented in court.

2. Failure to Introduce Tax Returns