Rule 607 provides, 'the credibility of a witness may be attacked by any party, including the party calling him.' In addition, they assert that a prior inconsistent statement of the witness may be admitted to attack his credibility even if the statement tends to directly inculpate the defendant. United States v. Miller, 664 F.2d 94, 97 (5th Cir. 1981), cert. denied, 459 U.S. 854, 103 S. Ct. 121, 74 L. Ed. 2d 106 (1982); United States v. Sisto, 534 F.2d 616, 622 (5th Cir. 1976); Williams v. United States, 394 F.2d 821 (5th Cir.), cert. denied, 393 U.S. 890, 89 S. Ct. 211, 21 L. Ed. 2d 169 (1968).
'A prosecutor may not use such a statement under the guise of impeachment for the primary purpose of placing before the jury substantive evidence which is not otherwise admissible.' Miller, supra at 97 (emphasis in original); Whitehurst v. Wright, 592 F.2d 834, 840 (5th Cir. 1979); United States v. Dobbs, 448 F.2d 1262 (5th Cir. 1971). Every circuit to consider this question has ruled similarly. See, e.g., United States v. Webster, 734 F.2d 1191, 1192 (7th Cir. 1984); United States v. Fay, 668 F.2d 375, ...