Sixth Amendment

As a corollary to the right of confrontation, the Sixth Amendment guarantees defendants the right to use the compulsory process of the judiciary to subpoena witnesses who could provide exculpatory testimony or who have other information that is favorable to the defense. The Sixth Amendment guarantees this right even if an indigent defendant cannot afford to pay the expenses that accompany the use of judicial resources to subpoena a witness (United States v. Webster, 750 F.2d 307 [5th Cir. 1984]). Courts may not take actions to undermine the testimony of a witness who has been subpoenaed by the defense. For example, a trial judge who discourages a witness from testifying by issuing unnecessarily stern warnings against perjury has violated the precepts of the Sixth Amendment (Webb v. Texas, 409 U.S. 95, 93 S. Ct. 351, 34 L. Ed. 2d 330 [1972]).

A statute that makes particular persons incompetent to testify on behalf of a defendant is similarly unconstitutional. At issue in Washington v. Texas, 388 U.S. 14, 87 S. Ct. 1920, 18 L. Ed. 2d 1019 (1967), was a state statute prohibiting accomplices from testifying for one another. Overturning the statute as a violation of the Sixth Amendment Compulsory Process Clause, the U.S. Supreme Court wrote that the defendant was denied the right to subpoena favorable witnesses "because the state arbitrarily denied him the right to put on the stand a witness who was physically present and mentally capable of testifying to events that he had personally observed and whose testimony was relevant and material to the defense."

Under certain circumstances, the prosecution may be required to assist the defendant in locating potential witnesses. In Roviaro v. United States, 353 U.S. 53, 77 S. Ct. 623, 1 L. Ed. 2d 639 (1957), the defendant was charged with the illegal sale of heroin to "John Doe." When the prosecution refused to disclose the identity of John Doe, the U.S. Supreme Court concluded that the Sixth Amendment had been abridged because the disclosure of Doe's identity may have produced "testimony that was highly relevant and … helpful to the defense."

Defendants also have a Sixth Amendment right to testify on their own behalf. Before the American Revolution, defendants were not permitted to take the witness stand in Great Britain and in many of the colonies. The common law presumed all defendants to be incompetent to give reliable or credible testimony on their own behalf because of their vested interest in the outcome of the trial. Each defendant, regardless of his innocence or guilt, was declared incapable of offering truthful testimony when his life, liberty, or property was at stake. The Sixth Amendment laid this common law rule to rest in the United States. The amendment permits, but does not require, a defendant to testify on his own behalf.