Taylor v. Illinois, 484 U.S. 400, is a United States Supreme Court decision in which the Court held that defense witnesses can be prevented from testifying under certain circumstances, even if that hurts the defense's case. Taylor was the first case to hold that there is no absolute bar to blocking the testimony of a surprise witness, even if that is an essential witness for the defendant, a limitation of the broad right to present a defense recognized in Washington v. Texas.