“ The rule we adopted in McCarthy has two purposes: (1) to insure that every defendant who pleads guilty is afforded Rule 11's procedural safeguards, which are designed to facilitate the determination of the voluntariness of his plea; (2) to provide a complete record at the time the plea is entered of the factors relevant to this determination, thereby facilitating a more expeditious disposition of a post-conviction attack on the plea. ”

“ In our recent decision of McCarthy v. United States, 394 U.S. 459, 89 S.Ct. 1166, 22 L.Ed.2d 418, we held that when a guilty plea is accepted in violation of Rule 11 the defendant must be afforded an opportunity to plead anew. Petitioner's plea was entered in 1954. The question we must decide, therefore, is whether McCarthy should be applied to guilty pleas accepted prior to the date of that decision. We hold that it should not. ”

“ Unquestionably, strict compliance with Rule 11 enhances the reliability of the voluntariness determination, and we have retroactively applied constitutionally grounded rules of criminal procedure designed to correct 'serious flaws in the fact-finding process at trial.' Stovall v. ”