Barker v. Wingo, 407 U.S. 514 (1972), was a case in which the United States Supreme Court held that determinations of whether or not the Sixth Amendment right to a speedy trial for defendants in criminal cases has been denied must be made on a case-by-case basis.
One factor recognized by the Court was the length of delay, but the Supreme Court has never explicitly ruled that some particular time limit must apply.