The polygraph, commonly called the lie detector, is not really an investigative technique
in and of itself. It is actually a form of interview. The polygraph is a mechanical device
designed to detect physiological changes that occur when a person makes an untruthful
statement. While many people firmly support the accuracy of the polygraph, the fact is
that it has little value as evidence in court. Indeed, only New Mexico routinely allows
polygraph examination results to be admitted in evidence in criminal trials. The U.S.
Supreme Court ruled in 1998 that a criminal defendant does not even have the right
to present evidence in his own defense that he has passed a polygraph test. Justice
Clarence Thomas ruled that there is “simply no consensus that polygraph evidence is
reliable.” He continued by stating that “to this day, the scientific community remains
extremely polarized” about the question.