The article focuses on the probation officer's presentence investigation report (PSR) as a multi-purpose document created by the officer to fulfill roles as prosecutor, investigator and witness, and adjudicative officer. Data are presented in the following categories: (1) Sentencing Procedures: Constitutional Procedure, Common Law Procedure, Federal Rules of Evidence; (2) The PSR¦s Traditional Role in Sentencing: Background, Federal Probation, The PSR; (3) The Sentencing Guidelines; and (4) Analyzing the PSR's Functions and Evidentiary Role: The PSR as a Charging Document, The PSR as an Exhibit Proving Criminal Conduct, The PSR as Akin to a Magistrate Judge's Report and Recommendation. Under the Sentencing Guidelines the PSR functions as a pleading, as an exhibit, and as a quasi judicial report. It has been transformed from a disinterested report to an adversarial one of multiple dimensions, affecting the way defendants and their counsel view the probation officer and the PSR. The defendant's impression that the probation officer is no longer a friend, advocate, or even neutral, will no doubt diminish his faith in the legitimacy of the Guidelines sentence. Footnotes