The Sixth Amendment to the U.S. Constitution guarantees the rights of the accused and helps to ensure a fair trial for defendants facing criminal prosecutions. According to About.com, it does this by ensuring that all persons accused of a crime have a speedy trial before an impartial jury.
The Sixth Amendment is one of several methods contained in the U.S. Constitution for protecting the accused from unfair treatment at the hands of the government. Originally ratified as part of the Bill of Rights, this amendment has since been applied by the Supreme Court to the states as part of the Due Process clause of the 14th Amendment, according to Wikipedia.
Wikipedia further explains that the Sixth Amendment ensures the protection of several distinct rights of the accused. First is the right to a speedy trial. The trial must also be public, though the Supreme Court found that this right is not absolute in the case of Sheppard v. Maxwell (1966), and it found that a degree of secrecy is warranted if publicity is judged to hurt the defendant's right to impartiality. An impartial jury is also guaranteed by this amendment, albeit for offenses that carry potential sentences of less than six months penal confinement.