The Facts
1. Trial by jury in serious criminal cases is guaranteed in the Sixth Amendment "in all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury..." and in the Constitutions of many states.
2. Supreme Court decisions interpreting the due process clause of the Fourteenth Amendment have applied the Sixth Amendment guarantee to state criminal cases. See Duncan v. Louisiana, 391 U.S. 145 (1968).
3. Trial by jury in most Federal civil suits is guaranteed by the Seventh Amendment. Similar provisions exist in many state Constitutions.
How Many on a Jury?
4. Traditionally, juries consisted of 12 members, who must reach a unanimous verdict. However, Supreme Court cases have held that the number 12 is not essential (Williams v. Florida, 399 U.S. 78, 1970, upheld the use of six-person juries in state criminal cases; see also Ballew v. Georgia, 435 U.S. 223, 1978). The Court's reasoning in Williams was that a six-person jury was "large enough to promote group deliberation, free from outside attempts at intimidation, to provide a fair possibility of obtaining a representative cross-section of the community." Many states have set numbers under 12 for particular types of cases.
Do Juries Have to Be Unanimous?
5. Traditionally, juries had to be unanimous, but the Supreme Court has upheld verdicts of 11-1, 10-2, and 9-3. See, for example Apodaca v. Oregon, 406 U.S. 404 (1972) and Johnson v. Louisiana, 400 U.S. 356 (1972). In Burch v. Louisiana, 441 U. S. 130 (1979), the Court did not uphold a 5-1 verdict.
Do Juries Have to Be Representative?
6. A series of Supreme Court cases has held that the requirement of an impartial jury means that jurors must be chosen from a representative cross section of the community, with no persons excluded on the basis or race, sex, or other impermissible factors. In Taylor v. Louisiana, 419 U. S. 522 (1975) the Court wrote "The purpose of a jury is to guard against the exercise of arbitrary power to make available the common sense judgment of the community as a hedge against the overzealous or mistaken prosecutor....This prophylactic vehicle is not provided if the jury pool is made up of only special segments of the populace."
The Role of Peremptory Challenges
7. Traditionally, lawyers on each side of a case, besides being able to challenge jurors "for cause", are allotted a certain number of peremptory challenges to jurors basically, hunches that a particular juror will not be favorable to their side. In recent years, courts, including the U.S. Supreme Court, have instituted procedures to see that these challenges are not used to impermissibly remove jurors of a particular ethnic group or gender. See Batson v. Kentucky, 476 U.S. 79 (1986).