[fn1] Under subsection (b)(1), the last date of the offense of conviction is the controlling date for ex post facto purposes. For example, if the offense of conviction (i.e., the conduct charged in the count of the indictment or information of which the defendant was convicted) was determined by the court to have been committed between October 15, 1991 and October 28, 1991, the date of October 28, 1991 is the controlling date for ex post facto purposes. This is true even if the defendant’s conduct relevant to the determination of the guideline range under §1B1.3 (Relevant Conduct) included an act that occurred on November 2, 1991 (after a revised Guideline Manual took effect).

Background: Subsections (a) and (b)(1) provide that the court should apply the Guidelines Manual in effect on the date the defendant is sentenced unless the court determines that doing so would violate the ex post facto clause in Article I, § 9 of the United States Constitution. Under 18 U.S.C. § 3553, the court is to apply the guidelines and policy statements in effect at the time of sentencing. Although aware of possible ex post facto clause challenges to application of the guidelines in effect at the time of sentencing, Congress did not believe that the ex post facto clause would apply to amended sentencing guidelines. S. Rep. No. 225, 98th Cong., 1st Sess. 77-78 (1983). While the Commission concurs in the policy expressed by Congress, courts to date generally have held that the ex post facto clause does apply to sentencing guideline amendments that subject the defendant to increased punishment.