When will a jury not instruct the jury on the statute of limitations regarding the conspiracy charge?

No request was made at trial for a statute of limitations instruction regarding the conspiracy charge, nor was an objection taken to the trial court's failure to give such an instruction to the jury. Citing United States v. Grammatikos, 633 F.2d 1013 (2d Cir.1980), and United States v. Cianchetti, 315 F.2d 584 (2d Cir.1963), the government contends that appellants therefore waived their right to raise the limitations defense on appeal. Grammatikos and Cianchetti, however, involved only a waiver of the right to appeal from a trial court's failure to instruct the jury on the statute of limitations. See Grammatikos, 633 F.2d at 1022; Cianchetti, 315 F.2d at 589. Neither holds that failure to object at trial to the lack of a statutory limitations instruction waives the underlying issue of whether there was sufficient evidence of the overt acts occurring within the statutory limitation period. Nonetheless, we hold that appellants may not now assert their statute of limitations claim for the first time.