Some courts have only six jurors because, according to U.S. federal law, a petit jury can have from six to 12 members to hear either civil or criminal cases. Civil trials often have six members, while juries at criminal trials usually have 12 members.
The U.S. Constitution affirms the right to a jury trial in federal court in Article III and the Sixth Amendment. The Seventh Amendment extends the right to civil cases with disputes over $20. However, the Seventh Amendment does not apply to state civil court trials, which are bound by state law. In 1868, the 14th amendment made jury trials for criminal cases a requirement in state courts as well. An 1898 ruling of the U.S. Supreme Court held that juries must be composed of 12 people. This was revised in 1970 to allow six-person juries. A decision in 1978 stated that a trial by a jury of less than six people denies a defendant due process of law. If a jury has more than six members, the illness of one jury member does not constitute a mistrial because there are still enough members to render a verdict.
State law determines the precise number of jurors in civil or criminal trials. When jurors are first selected, they typically complete questionnaires to determine if they have basic qualifications for jury duty. Prospective jurors receive a summons and appear for a process called "voir dire." They are questioned by the judge and attorneys in the case to assess their impartiality. From the jury pool, the six- to 12-member jury and a number of alternates are chosen.