I've heard about this like with people making up something in their head and they'll say yes or no, though it's a lie, but to test won't pick it up. Fact or fiction?
Polygraphs are known to be unreliable. People who take certain drugs (such as beta blockers or tranquilizers) may be able to lie and pass a polygraph exam, and pathological liars may also be able to fool the machine.
Polygraph test are not accurate to begin with, and the results can not be used in court due to the inaccuracy. So yes, you can fool a polygraph test, and there is no way of a machine determining if you are telling the truth or lying.
