In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defense.
Like with other provisions of the Bill of Rights, the application of the Sixth Amendment evolved. In considering a bill of rights in August 1789, the House of Representatives adopted a proposal to guarantee a right to a jury trial in state prosecutions but the Senate rejected the proposal, and the 1869 case of Twitchell v. Commonwealth ended any doubt that the states were beyond the direct reach of the Sixth Amendment.
The reach of the Amendment thus being then confined to federal courts; questions arose as to its application in federally established courts not located within a state. The Court found that criminal prosecutions in the District of Columbia and in incorporated territories must conform to the Amendment, but those in the unincorporated territories need not.
The Sixth Amendment applies in criminal prosecutions. Only those acts that Congress has forbidden, with penalties for disobedience of its command, are crimes. Contempt proceedings, which at one time were not considered criminal prosecutions, are now considered to be criminal prosecutions for purposes of the Amendment.
The function of voir dire is to give the defense and the prosecution the opportunity to inquire into, or have the trial judge inquire into, possible grounds of bias or prejudice that potential jurors may have, and to acquaint the parties with the potential jurors.
The judge must determine whether the nature and strength of the opinion . . . raise the presumption of partiality.
Constitution Annotated. Analysis and Interpretation of the U.S. Constitution (n.d.). Amdt 6.1 Overview of Sixth Amendment, Right to a speedy trial.