Respondent was convicted in a United States District Court of an assault with intent to murder, an offense punishable under 18 U.S.C. § 113(a) 'by imprisonment for not more than twenty years.' Desiring more detailed information as a basis for determining the sentence to be imposed, the trial judge decided to proceed 'under the flexible provisions of (s) 4208' of 18 U.S.C. Accordingly, he committed respondent to the custody of the Attorney General to await a study by the Director of the Bureau of Prisons of respondent's previous delinquency, criminal experience, social background, etc. His order provided that after the results of the study and the Director's recommendations were reported to the court, respondent's commitment, deemed to be for 20 years, would 'be subject to modification in accordance with Title 18 U.S.C. 4208(b).'
After the Director's report was received, the trial court entered an order providing 'that the period of imprisonment heretofore imposed be reduced to Five (5) years' and that the Board of Parole might decide when the respondent should be eligible for parole. Neither respondent nor his counsel was present when this modification of the court's previous commitment under § 4208(b) was entered. No direct appeal was taken, but respondent moved to vacate sentence under 28 U.S.C. § 2255. The trial court denied relief, but the Court of Appeals reversed and remanded with directions to vacate the sentence on the ground that it was error for the district judge to impose the final sentence under § 4208(b) in the absence of petitioner and his counsel. In another case, Corey v. United States, 307 F.2d 839, the Court of Appeals for the First Circuit held that it was the original commitment under § 4208(b), not the fixing of the final sentence, which marked the point from which time to appeal began running. Because of the disagreement between the two appellate courts' interpretation of § 4208(b) and the general confusion in District Court's and Courts of Appeals as to this section's exact meaning and effect, we granted certiorari in both cases.