United States v. Scheffer, 523 U.S. 303 (1998), was the first case in which the Supreme Court issued a ruling with regard to the highly controversial matter of polygraph, or "lie-detector," testing.

At issue was whether the per se exclusion of polygraph evidence offered by the accused in a military court violates the Sixth Amendment right to present a defense.

[1] The United States v. Scheffer ruling came, as legal writer Joan Biskupic noted in the Washington Post, "at a time when polygraph machines are increasingly being used outside the courtroom" — and inside as well.

Employers were using them to test job applicants with regard to past wrongdoing, and to monitor present jobholders as well (although this practice was mostly outlawed in 1988 by the Employee Polygraph Protection Act).

While the latter practice might raise Fourth Amendment questions of its own, the use of polygraph results in the courtroom had become a battleground for opposing factions of evidentiary experts.