The Sixth Amendment to the United States Constitution guarantees that “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.” The Sixth Amendment goes on to preserve other rights for criminal defendants, but says nothing else about what a “trial by an impartial jury” entails.

The United States Supreme Court has held that the Sixth Amendment right to a jury trial—which also applies to the states by way of the Fourteenth Amendment—requires a unanimous verdict to convict a defendant of a serious offense in state or federal court. A serious offense is generally a felony offense, or a misdemeanor in which the defendant may be sentenced to a year or more in jail or prison.

In Massachusetts, as in all states, the Sixth Amendment's guarantee of a 'speedy and public trial, by an impartial jury' is upheld. This means that in criminal prosecutions, defendants have the right to have their case decided by a jury of their peers from the area where the crime occurred. The requirement for a unanimous verdict to convict a defendant of a serious offense, as interpreted by the United States Supreme Court, is also applicable in Massachusetts. A serious offense typically refers to felonies, which are more severe crimes, and misdemeanors that carry a potential sentence of a year or more in jail or prison. The unanimity requirement ensures that all members of the jury agree on the verdict, whether it is to convict or acquit, in cases involving these more serious charges. This standard is applied in both state and federal courts, with the right to a jury trial extended to the states through the Fourteenth Amendment.