Michael Williams (defendant) was sentenced to death for murder. Williams sought a writ of habeas corpus in federal district court requesting an evidentiary hearing on three constitutional claims that he claimed he had been unable to develop in state court. Those claims were that the government withheld a witness’s psychiatric evaluation, that a juror did not reveal potential bias, and that a prosecutor knew of the juror’s potential bias. The district court dismissed the petition. The court of appeals affirmed, finding that federal law as amended by the Antiterrorism and Effective Death Penalty Act of 1996 barred an evidentiary hearing if a defendant was unable to develop the factual basis of his claim in state court proceedings. Williams appealed to the United States Supreme Court, which granted certiorari.