Module 5 - Polygraph Testing & Forensic Document Analysis

Examples of Polygraph Readings

Determining whether a subject has been truthful during a polygraph exam is based upon the physiological readings.  During stress, the sympathetic nervous system increases the blood pressure, breathing, the heart rate, and perspiration.  When a subject decides to give an untruthful answer to a question, this deception causes some stress.  This results in a noticeable change in the physiological measurements recorded by the polygraph instrument.  If a subject gives an honest answer, no noticeable change will be evident in the physiological measurement readings.

Example A: Simulated Polygraph Reading from a Truthful Suspect

Below is an example diagram of two physiological readings from a polygraph instrument.  No noticeable changes or fluctuations in the measurements appear; the reading appears to be consistent.

Example B: Simulated Polygraph Reading from a Deceptive Suspect

Below is another example diagram of two physiological readings from a polygraph instrument.  The fluctuations in the measurements after questions #2 and #4 indicate that the subject did not answer these two questions truthfully.

Did you know?

"A lie with a purpose is one of the worst kind and the most profitable."

- Josh Billings

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