The Speedy Trial Clause of the Sixth Amendment to the United States Constitution provides that "[i]n all criminal prosecutions, the accused shall enjoy the right to a speedy . . . trial . . . ." The Clause protects the defendant from delay between the presentation of the indictment or similar charging instrument and the beginning of trial.
In Barker v. Wingo (1972), the Supreme Court developed a four-part test that considers the length of the delay, the reasons for the delay, the defendant's assertion of his right to a speedy trial, and the prejudice to the defendant. A violation of the Speedy Trial Clause is cause for dismissal with prejudice of a criminal case.
In addition to the constitutional guarantee, various state and federal statutes confer a more specific right to a speedy trial. The prosecution must be "ready for trial" within six months on all felonies except murder, or the charges are dismissed by action of law without regard to the merits of the case. This is also known as a "ready rule".
The federal law detailing this right is the Speedy Trial Act of 1974. All U.S. states have either statues or constitutional provisions detailing this right.