A grand jury was convened to investigate possible illegal gambling. The grand jury received voice recordings as part of the investigation. The grand jury subpoenaed Dionisio (defendant) and several other individuals and ordered them to provide a voice sample for comparison with the recordings. Dionisio refused to provide a voice sample. The United States (plaintiff) filed a motion to compel compliance with the subpoena. Dionisio argued that compelled production of the voice sample violated his rights under the Fifth Amendment and Fourth Amendment. The district court ruled in favor of the United States and ordered Dionisio to provide a voice sample. Dionisio refused, and the district court found him in contempt. Dionisio appealed the contempt order. The court of appeals concluded that the subpoena constituted an unreasonable search and seizure and reversed the district court's order. The United States Supreme Court granted certiorari.