concurring.
While I have no doubt that the defendant in this case has been treated fairly, I agree with my colleagues that the combination of the district judge’s unfortunate slip of the tongue during the change-of-plea hearing and his frank use of information elicited from the defendant during debriefing to impose a sentence at the top of the guideline range creates a perception of unfairness and requires vacation of the sentence. I write separately, however, to highlight four points.
*18First, this is not a case in which the court coaxed a plea through a misrepresentation. Mr. Conway is an intelligent, well-educated businessman who was represented throughout by distinguished counsel. Insofar as I can tell, he was not actually misled and the judge’s lapsus linguae had no actual effect on the course of the proceedings.4 Nevertheless, I cannot vote to uphold the sentence. When the public perception of justice is imperilled by the court’s actions in a criminal case, the usual rules of harmless error do not apply.
Second, it is important to emphasize that this case is sui generis. Under ordinary circumstances, the guidelines permit information obtained from a cooperating defendant during debriefing to be used in determining the defendant’s sentence (as long as the plea agreement does not impose a further limitation on these uses). See U.S.S.G. § 1B1.8(b)(5) & n. 1.
Third, the' plea agreement in this case, interpreted under principles of contract law, see United States v. Hogan, 862 F.2d 386, 388 (1st Cir.1988), imposed no such special limitation. Were it not for the judge’s inadvertent misstatement during the change-of-plea colloquy, the court could have used the information obtained during debriefing either to deny the downward departure, or to fix the defendant’s sentence within the appropriate guideline range, or for both purposes.
Fourth, under the plea agreement, the guidelines, and binding precedent in this cir-. euit, see United States v. Mariano, 983 F.2d 1150, 1157 (1st Cir.1993), the district court was obliged fully to consider the elicited information in determining whether to grant the government’s section 5K1.1 motion for a downward departure. On remand, the district court remains obliged to consider all the information. And, moreover, even if the court finds that the defendant substantially assisted the investigation, it is not obligated to grant the section 5K1.1 motion and depart downward, see Mariano, 983 F.2d at 1156-57, or, alternatively, to impose a sentence at the bottom of the guideline range.
Despite the court’s substantial discretion in these respects, I agree with my colleagues that resentencing is required. When, as now, a sentencing court makes clear that a discretionary action — even a discretionary action that the court has no legal obligation to explain at all5 — is premised on an impermissible consideration, the court of appeals must intervene. See United States v. Drown, 942 F.2d 55, 60 (1st Cir.1991). To this extent, the judge pays a high price for candor — but justice demands the exaction.
. This conclusion is underscored, if not compelled, by the late blossoming of any argument based on the court’s misstatement at the change-of-plea hearing. The defendant's brief on appeal is devoid of developed argumentation in this regard, and the judge’s statement was first mentioned at oral argument in this court (and then, only in passing).
. A good example, apropos here, is that, subject to certain exceptions not relevant in the circumstances at bar, a sentencing court has no legal obligation to explain why it chooses a particular sentence within a narrowly defined guideline sentencing range. See, e.g., United States v. Levinson, 56 F.3d 780, 780 (7th Cir.1995); United States v. Garrido, 38 F.3d 981, 986 (8th Cir.1994); United States v. Lively, 20 F.3d 193, 198 (6th Cir.1994). By like token, a sentencing court customarily need not explain the basis for its refusal to depart downward. See, e.g., United States v. Lombardi, 5 F.3d 568, 572 (1st Cir.1993).