"The federal government polygraphs about 70,000 people a year for security clearances and jobs, but most courts won’t allow polygraph results to be submitted as evidence, citing the machines’ unreliability. Scientists question whether polygraphers can identify liars by interpreting measurements of blood pressure, sweat activity and respiration. Researchers say the polygraph-beating techniques can’t be detected with certainty, either.

Citing the scientific skepticism, one attorney compared the prosecution of polygraph instructors to indicting someone for practicing voodoo.

“If someone stabs a voodoo doll in the heart with a pin and the victim they intended to kill drops dead of a heart attack, are they guilty of murder?” asked Gene Iredale, a California attorney who often represents federal defendants. “What if the person who dropped dead believed in voodoo?"