Can the prosecution impeach appellant with incriminating statements taken in violation of the Sixth Amendment right to counsel?

The state court, however, permitted the prosecution to impeach appellant with incriminating statements taken in the absence of counsel. We are constrained to hold that this decision was constitutionally infirm. In United States v. Brown, 699 F.2d 585 (2 Cir.1983), we held that the government had a "heavy burden" of proving that any inculpatory statements taken in violation of the Sixth Amendment right to counsel were voluntarily given after a valid waiver of that right. We held that, absent a valid waiver, the use of a statement taken in derogation of a defendant's right to counsel was absolutely prohibited, not only in the government's case-in-chief, but as impeachment evidence as well. Id. at 590. In the instant case, there was no waiver of appellant's right to counsel prior to the taking of the incriminating statements. Accordingly, we hold that it was constitutionally erroneous to permit the state to introduce those statements through rebuttal testimony for impeachment purposes.