Does a probation officer have a constitutional obligation to provide counsel for a defendant at sentencing?

7 See, e.g., United States v. Chanen, 549 F.2d 1306, 1313 (9th Cir.1977), cert. denied, 434 U.S. 825, 98 S.Ct. 72, 54 L.Ed.2d 83 (1977) (noting that courts must beware of exercising their supervisory power to prescribe rules of conduct for prosecutors, because such an exercise "could readily prove subversive of the doctrine of separation of powers").

8 Our holding should not be read to imply that probation officers generally discharge their duty with anything less than complete impartiality. However, the fact that the probation officer is not the defendant's adversary does not diminish the importance to the defendant of the presentence interview. Indeed, a defendant's constitutional right to be represented by counsel at sentencing is based upon "the critical nature of sentencing in a criminal case," Mempa v. Rhay, 389 U.S. 128, 134, 88 S.Ct. 254, 257, 19 L.Ed.2d 336 (1967), notwithstanding the fact that the judge who presides over sentencing is, like the probation officer, presumed to be completely impartial.