How have the courts interpreted the federal sentencing guidelines in sentencing enhancement cases?

Grant argues that unconstitutional state court convictions were used for purposes of sentence enhancement. A district court's finding as to whether a defendant had a prior conviction is reviewed for clear error. United States v. Gross, 897 F.2d 414, 416 (9th Cir.1990), overruled on other grounds by United States v. Palmer, 946 F.2d 97 (9th Cir.1991). Interpretation of the Sentencing Guidelines are reviewed de novo. United States v. Anderson, 942 F.2d 606, 609 (9th Cir.1991) (en banc).

Grant does not dispute that he pleaded guilty to all three charges. He does, however, claim that all three convictions are invalid for purposes of sentencing enhancement because he had not been apprised of his constitutional rights prior to pleading guilty. A conviction is constitutionally invalid if the defendant does not knowingly and voluntarily waive his right to trial by jury, to confront the witnesses against him, and to remain silent. Boykin v. Alabama, 395 U.S. 238, 242-243 (1969).