In what circumstances will the prosecution improperly refer to missing evidence in its argument to the jury at trial?

Finally, the petitioner contends that the prosecution improperly referred to missing evidence in its attempt to persuade the jury that petitioner's experts were not to be believed and there was nothing to support the conclusion that the death was accidental. Petitioner, however, did not object to the prosecutor's comments. In the absence of such an objection, the remarks tending to shift the burden of proof in the jurors' minds cannot violate due process unless it can be shown that they were of a character to "undermine fundamental fairness." Mitchell v. Goldsmith, 878 F.2d 319, 324 (9th Cir.1989). During trial both parties attempted to use the absence of the evidence as support for their arguments.