discussed Cited "see" United States v. Sisson (2×) See infra, at 306. [52] See 396 U. S. 812 (1969). [53] At common law, a special plea in bar was ordinarily used to raise three defenses— autrefois acquit, autrefois convict, and pardon— and there is language in some of our cases that indicates that, apart from these defenses, a plea in bar was not appropriate "to single out for determination in advance of trial matters of defense either on questions of law or fact," United States v. Murdock, 284 U. S. 141, 151 (1931).