Where defendant did not object at trial, but raised the issue for the first time on appeal, the federal appellate court held that the prosecutor did not commit misconduct by “vouching” for the prosecution witness. Although the prosecutor questioned the witness about his agreement to testify for the government and introduced the written agreement into evidence, he did not question the witness regarding his obligation under the contract to testify truthfully, and when the witness referred to that obligation, the prosecutor steered him away from testifying about that. Moreover, the prosecutor questioned the witness at length about his criminal history. Under these facts, the district court did not commit plain error in permitting the prosecutor to elicit this testimony. Where defendant did not object at trial, but raised the issue for the first time on appeal, the federal appellate court held that the prosecutor did not commit misconduct by “vouching” for the prosecution witness. Although the prosecutor questioned the witness about his agreement to testify for the government and introduced the written agreement into evidence, he did not question the witness regarding his obligation under the contract to testify truthfully, and when the witness referred to that obligation, the prosecutor steered him away from testifying about that. Moreover, the prosecutor questioned the witness at length about his criminal history. Under these facts, the district court did not commit plain error in permitting the prosecutor to elicit this testimony. The federal sentencing issues raised and decided were not summarized. The district court did not err in refusing to instruct the jury to consider the prosecution’s witness, who had received leniency in exchange for his testimony, that his testimony should be viewed with “greater caution” per Ninth Circuit Model Jury Instruction 4.9. The instruction the court gave, stating that the testimony of that witness “should be received with caution” did not materially affect the verdict or constitute error seriously affecting the fairness or integrity of the trial.