What is the test for a prosecutor's argument in a civil case?

Flake's reliance on United States v. Roberts, 618 F.2d 530 (9th Cir.1980) is misplaced. The prosecutor here did not "place the prestige of the government behind the witness or ... indicate that information not presented to the jury supports the witness's testimony." Id. at 533. Instead, in self-defense, he asked the jury to disregard defense counsel's insinuation that the government had intentionally deceived the jury in producing testimony that immunity had not been granted. Under these circumstances, the prosecutor's argument was proper.