"The Sixth Amendment promises that [i]n 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. The Amendment goes on to preserve other rights for criminal defendants but says nothing else about what a trial by an impartial jury entails.
"Still, the promise of a jury trial surely meant something otherwise, there would have been no reason to write it down. Nor would it have made any sense to spell out the places from which jurors should be drawn if their powers as jurors could be freely abridged by statute. Imagine a constitution that allowed a jury trial to mean nothing but a single person rubberstamping convictions without hearing any evidencebut simultaneously insisting that the lone juror come from a specific judicial district previously ascertained by law. And if thats not enough, imagine a constitution that included the same hollow guarantee twicenot only in the Sixth Amendment, but also in Article III.8 No: The text and structure of the Constitution clearly suggest that the term trial by an impartial jury carried with it some meaning about the content and requirements of a jury trial.
"One of these requirements was unanimity. Wherever we might look to determine what the term trial by an impartial jury trial meant at the time of the Sixth Amendments adoptionwhether its the common law, state practices in the founding era, or opinions and treatises written soon afterwardthe answer is unmistakable. A jury must reach a unanimous verdict in order to convict. "
Very convincing!