Failing Driver's Test Prank

SOLVED: Polygraph lie-detector machines are commonly used in criminal investigations. The device measures nervous excitement, operating on the idea that if a person is telling the truth they will remain calm.The American Polygraph Association claims that polygraphs accurately identify liars 90% of the time. In other words, if a person lied the test results will be positive 90% of the time.Although the polygraph test is good at identifying liars, there is a 50% chance that the polygraph test will

Polygraph screen, printed graphs and open subject's hands.

Polygraph Machine: What are they and how do they work?

The FBI and other agencies are using polygraphs to find leakers. But do they work?