Against a backdrop of accelerating developments in the science of lie detection certain to reopen the debate on the reliability and therefore admissibility of lie detector evidence in the federal courts, this Article examines whether the prohibition on hearsay evidence (or other evidentiary objections) will preclude admissibility of even scientifically reliable lie detector evidence. The Article concludes that the hearsay prohibition, which has been largely ignored by courts and commentators, is the primary obstacle to the future admission of scientifically valid lie detector evidence. The Article also suggests a potential solution to the hearsay problem that may allow admission of lie detector evidence in narrowly defined circumstances.