FAQs polygraph

Scientific and Modern Polygraph FAQ

1. What is a polygraph?

A polygraph is a computerized biomedical instrument designed to record physiological changes associated with the psychological processes of truth-telling and deception.
The term comes from the Greek poly (many) and graphein (writings), referring to the instrument’s ability to produce multiple simultaneous tracings.

A practical analogy:

A polygraph functions like a behavioral electrocardiogram—measuring physiological patterns rather than detecting lies directly.

2. What does the polygraph record?

Modern polygraphs record 5 to 10 physiological channels, including:

Channel Scientific Description What It Indicates

Thoracic Pneumograph Sensor around the chest Respiratory activity

Abdominal Pneumograph Sensor around the abdomen Rhythm and depth of breathing

Electrodermal Activity (EDA/GSR) Plates on fingers or palms Sympathetic activation (sweat gland activity)

Photoplethysmograph (PPG) Finger sensor Peripheral vascular changes

Cardiovascular Channel Calibrated BP cuff Pulse and variability

Movement Sensor Accelerometer Detection of physical countermeasures

These channels capture micro-variations that reflect cognitive load, emotional activation, and behavioral responses during the test.

3. Whose side is the examiner on?

A polygraph examiner is a neutral scientific evaluator, similar to a radiologist interpreting imaging data.
Their role is to determine whether the physiological data aligns with truthful or deceptive responses—never to advocate for any party.

4. Is the examination confidential?

Yes. All information is covered by applicable privacy laws and a signed confidentiality agreement.
Only authorized recipients receive the final report.

5. Can someone be forced to take a polygraph?

Legally and ethically: no.
Polygraph testing requires voluntary cooperation.
However, certain careers, licenses, and judicial processes may require polygraph testing as part of eligibility criteria.

6. Does the polygraph cause discomfort?

Modern instruments use low-pressure cuffs and ergonomic sensors, making discomfort rare.
Most individuals describe the experience as neutral.

7. How long does a polygraph examination take?

Most exams last 90–120 minutes, typically divided as follows:

PhaseDurationPurpose

Pre-test interview45–60 min. History review, explanations, question formulation

In-test phase10–20 min. Data collection

Post-test phase10–20 min. Preliminary discussion and clarifications

Complex or multi-issue cases may take longer.

8. How many questions are asked?

This depends on the validated technique used (e.g., Utah ZCT, DLST, MGQT).
Typically:

2–4 relevant questions
comparison questions
neutral or technical questions

Each series consists of about 10–12 question presentations.
There are no surprise questions; all wording is reviewed before hand.

9. Can nervousness affect the results?

All examinees feel nervous—that is expected.
Polygraph scoring evaluates changes from the individual’s baseline, not the absolute level of nervousness.

Analogy:

Anxiety is like normal city noise—always present, but what matters are the sudden spikes.

Scientific evidence shows nervousness does not cause truthful people to fail nor does it let deceptive individuals pass.

10. Does fatigue affect the test?

Normal fatigue does not interfere.
Only extreme fatigue or illness may warrant rescheduling.

11. How should I prepare for a polygraph?

Maintain your usual routine.
Get adequate rest.
Avoid arriving hungry or in pain.
Take your prescribed medications normally.
Avoid excessive caffeine or stimulants.
Keep your schedule free during the exam time.
Be prepared to collaborate openly.

12. Can someone accompany me?

Yes, to the testing site.
However, only the examinee enters the testing room unless an interpreter or guardian is essential.
Sessions may be recorded if both parties agree.

13. Can someone beat a polygraph?

Theoretically, any human-made system can be manipulated.
In practice:

Modern polygraphs include countermeasure detection sensors.
Success rates for countermeasures are low.
Research shows truthful individuals who attempt countermeasures often reduce their chances of passing.

Attempts typically cause more harm than good.

14. When will I know the results?

After the test, the examiner evaluates the data and provides a diagnostic opinion.
If independent quality control is required, an initial verbal summary may be followed by a final written report.

15. What is the Employee Polygraph Protection Act (EPPA)?

EPPA is a U.S. federal law that restricts the use of polygraphs by most private employers, with specific exemptions (e.g., security-sensitive industries).
It prohibits requiring or requesting employees/applicants to take a polygraph except under defined circumstances.

16. Are polygraph results admissible in court?

This varies by jurisdiction:

Often admissible only if both parties stipulate before hand.
New Mexico allows admission without stipulation in certain cases.
Some courts evaluate admissibility on a case-by-case basis.

17. Are voice stress analyzers a reliable alternative?

No.
Scientific reviews consistently show that voice stress devices lack valid and reliable accuracy.
Many systems disappear from the market after independent evaluation reveals poor performance.