Typically, a person who is lying or deceiving others will experience guilt and anxiety.
These emotions produce physiological arousal in the body
leading to characteristic changes in body posture and movements
as well as specific gestures or facial expressions.
Unfortunately, most people are not very good at reading these nonverbal cues
or using them to detect deception
The most common method of lie detection involves using a polygraph to record the activity of the sympathetic nervous system
by measuring heart rate, perspiration, breathing rate, and other physiological responses.
Polygraph examiners ask “control questions” to establish baseline rates of activity
then ask “relevant questions” to see if the level of arousal changes.
If a suspect shows more nervousness while answering relevant questions
that person would be judged as lying.
Research suggests that the judgments of polygraph examiners are correct only about two-thirds of the time.
Examiners make two kinds of errors: misses (judging guilty people as innocent)
The high false alarm rate is the main reason that polygraph evidence is not admissible in court.