When a defendant raises an issue on appeal that was not raised before the judge, the court of appeals may review for plain error. See Fed.R.Crim.P.52(b). "A plain error is a highly prejudicial error affecting substantial rights." U.S. v. Giese, 597 F.2d 1170, 1199 (9th Cir.), Cert. Denied, 444 U.S. 979 (1979). Plain error is invoked to prevent a miscarriage of justice or to preserve the integrity and the reputation of the judicial process. U.S. v. Smith, 962 F.2d 923, 935 (9th Cir. 1992).