Can a person fail a polygraph because of high blood pressure or nervousness?
No. Polygraph is not designed to record or measure nervousness. While a person's heart beat and respiration rate may increase when he or she is nervous, a qualified examiner understands this, and will take it into consideration when evaluating an examinee's response. Unlike general nervous tension, an examinee's reaction to deceptive responses is highly specific. An examiner mitigates a nervous response by reviewing the questions with the examinee and through an acquaintance or "practice test" prior to the exam.