What is a polygraph?

A polygraph is an instrument that records various physiological changes in the body of the examinee while he or she is asked specific questions. These questions can cause a psychological response which causes the examinee’s body to react. These physiological responses in respiratory, electro-dermal and cardiovascular activity are then recorded.

How much does a polygraph exam cost?

The cost will vary depending on the complexity of the case. More complex cases require a significant amount of time, which increases the cost. Be aware that all polygraph examinations are not equal, and any examiner offering to complete an examination for a significantly reduced price should be thoroughly vetted. This will entail checking what equipment they use, whether software updates have been done, if they have completed their training through a recognised training school, and if they have the necessary accreditation to perform the test and interpret the results. If the issue is important enough to get a polygraph, it’s important enough to get a good quality examiner!.

What happens during a polygraph examination?

The polygraph examiner first confers with the client, or investigators read any reports in connection with the incident, and they then plan the polygraph test.

Pre-Test Interview:

The examiner will:

  • Advise the examinee of his or her rights (both legal & polygraph rights)
  • Discuss the case facts with the examinee
  • Assess the examinee’s ability to take the polygraph test (mental & medical history).
  • Ask the examinee to sign the consent form, as well as all other relevant forms used during the polygraph test.
  • Conduct a forensic assessment interview.
  • Generate and review all test questions in order to prevent extraneous reactions. This will:
    1. Prevent novelty.
    2. Prevent cognitive activity.
    3. Remove ambiguities from relevant questions.
    4. Focus psychological set.

Examinees are informed of the purpose of the testing and the testing procedure. After confirming that they understand, examinees willingly consent to polygraph testing and the audio-visual recording thereof (if required).

Examinees respond to questions concerning their suitability for testing, and in the opinion of the examiner, examinees are determined as suitable subjects for testing.

An acquaintance test can be conducted to familiarise the examinee with the testing process.

The acquaintance test will proof to the examinee that the polygraph instrument is able to detect a lie, when instructed to tell a lie. The innocent examinee now believes that the polygraph instrument will proof his or her innocence. The guilty examinee now knows that there is no way that he or she can lie during the polygraph test. The acquaintance test also allows the examinee to get use to the specific instruments that has been attached to his or her body.

In-Test Phase

We record physiological data, a minimum of three (3) charts.

Chart Interpretation

Examinees’ level of nervousness or reactivity is not explicitly compared against other people, but only against themselves; they thus act as their own controls. The examiner evaluates examinees’ physiological changes and renders an opinion of ‘Truth’ or ‘Deception’.

Post Polygraph Interview

When appropriate, examinees will be given the opportunity to explain any physiological responses to one or more of the questions. The results will be given to the client as soon as practical, with a written report to follow.

How does a polygraph work?

Respiratory activity is recorded by placing two expandable sensor tubes on the examinee. One tube is placed on the examinee’s chest above the heart, and the second is placed around the abdomen. The Galvanic Skin Response, or sweat gland activity, is recorded by attaching two small metal plates to two of the fingers. Cardiovascular changes are recorded by using a blood pressure cuff. All those micro changes are recorded while the examinee is asked a series of questions. Examinees’ responses to questions are given a numerical score using criteria standard for the polygraph technique that is being used.

PSYCHOLOGICAL SET: Signal value - Fear of detection

Innocent Examinee

Innocent examinees answer the relevant questions truthfully. They lie to, or are doubtful of, the comparison questions, which now have greater signal value. They thus react more or greater to the comparison questions than relevant questions.

Guilty Examinee

TGuilty examinees lie to both the comparison questions and relevant questions, but are more concerned about their lies to the relevant questions, because of these questions’ signal value and their fear of detection.
They thus react more to relevant questions than to the comparison questions.

Questions types

  1. Relevant questions focus directly on the matter under investigation. For example: “Did you commit this crime?”
  2. Irrelevant questions are completely unrelated to the matter under investigation. For example: “Is today Wednesday?”
  3. Comparison questions are only indirectly related to the matter being investigated. The question is designed to either provoke a lie, or to create concern about whether or not the examinee is concealing information from the examiner. For example: “Before the age of 20, have you ever deliberately told a serious lie, to someone that trusted you?”

What questions will be asked during the examination?

That depends upon the case. We will review all the questions with the examinee prior to the examination. There are no surprise questions.

How accurate is a polygraph?

This is taken from the American Polygraph Association (APA) website:

‘… scientific evidence supports the validity of polygraph examinations that are conducted and interpreted in compliance with documented and validated procedure. Thus, such examinations have great probative value and utility for a range of uses, including criminal investigations, offender management, and selection of applicants for positions requiring public trust. The APA Standards of Practice set some of the highest professional requirements for its members to ensure their polygraph services are valuable, reliable, and promote ethically responsible practices. The APA also produces a variety of model policies that represent the current understanding of best practices, and makes them widely available so that polygraph examiners (both APA members and non-members) and their clients can be aware of what constitutes a valid examination process. The APA believes that well informed departments, agencies, and clients will insist on APA members for their polygraph services.

Recently the APA undertook an exhaustive review of all of the peer-reviewed publications on polygraph testing that represented field practices and which met the requirements of the APA Standards of Practice. A meta-analysis was conducted, and a report was completed in late 2011. An executive summary of the report is freely available to the public through this website. Please visit the Executive Summary of the Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques page to download the summary and FAQ section.

The executive summary reports that 38 studies satisfied the qualitative and quantitative requirements for inclusion in the meta-analysis. These studies involved 32 different samples, and described the results of 45 different experiments and surveys. They included 295 scorers who provided 11,737 scored results of 3,723 examinations, including 6,109 scores of 2,015 confirmed deceptive examinations, 5,628 scores of 1,708 confirmed truthful exams. Some of the cases were scored by multiple scorers and using multiple scoring methods. The data showed that techniques intended for event-specific (single issue) diagnostic testing produced an aggregated decision accuracy of 89% (confidence interval of 83% – 95%), with an estimated inconclusive rate of 11%. Polygraph techniques in which multiple issues were encompassed by the relevant questions produced an aggregated decision accuracy of 85% (confidence interval 77% – 93%) with an inconclusive rate of 13%. The combination of all validated PDD techniques, excluding outlier results, produced a decision accuracy of 87% (confidence interval 80%– 94%) with an inconclusive rate of 13%. These findings were consistent with those of the National Research Council’s (2003) conclusions regarding polygraph accuracy, and provide additional support for the validity of polygraph testing when conducted in accordance with APA Standards of Practice.’
Taken from: www.polygraph.org/polygraph-validity-research

What types of polygraph examination are there?

There are generally two main types of polygraph examinations that are used, but a number of others exist for specific circumstances. The first is a multiple-issue examination, which allow for a larger scope of questions, but are considered less accurate. The second is a specific issue examination, which is considered the most accurate, but is limited in scope to one specific issue.

To simplify the types of polygraph examinations commonly used, we have placed them in the following three categories:

i) Pre-Employment Polygraph Test:

  • Work history details
  • Prior criminal activity and convictions
  • Narcotic and Alcohol abuse

ii) Periodic Polygraph Tests:

Employees are tested periodically to establish on-going truthfulness and honesty, and these tests can assist in identifying risks.

iii) Specific Polygraph Tests:

  • Fraud
  • Collusion
  • Theft
  • Criminal Activity
  • Assault
  • Private Issues
  • Event participation compliance – i.e. drug taking

How can you best prepare to take a polygraph?

It is suggested that examinees get a good night’s rest the night before the testing. They should have a light meal or snack before coming in, and avoid large amounts of caffeine. Examinees should follow their usual routine. It’s also recommended that 24 hours prior to the test, they avoid an overindulgence of alcohol or use of any illegal substances. If at all possible, they should try to avoid any arguments or emotional strain. It’s very important that they continue to take any prescribed medication as usual. The examinees should also wear something they feel comfortable in.

Who gets the results of the examination?

Examinations and consultations are private and confidential. Polygraph results will only be released to authorised personnel.

Will the medication(s) that are prescribed by my doctor, affect the results of my examination?

Examinees should continue to take medications as prescribed by their doctor. Some medications can affect the physiological response in your body. Examinees should notify us of current medications so that their suitability for examination assessment can be determined.

IMPORTANT NOTE: Examinees should not take any illegal drugs or alcohol before the examination!

Will nervousness affect the results?

It is expected that all examinees will feel a level of nervousness. This is completely normal. Being nervous will not cause deceptive results.

The following services are also available as part of the polygraph examination:

  • Criminal Checks
  • ITC Checks – Company Checks
  • Company Screenings