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From the Archives: Interview with a Polygraph Examiner

Posted by Writing PIs on April 10, 2016

American inventor Leonarde Keeler (1903-1949) testing his lie-detector on Dr. Kohler, a former witness for the prosecution at the trial of Bruno Hauptmann, 1937 (image is in the public domain)

American inventor Leonarde Keeler (1903-1949) testing his lie-detector on Dr. Kohler, a former witness for the prosecution at the trial of Bruno Hauptmann, 1937 (image is in the public domain)

Below is an interview Colleen did back in 2005 with Lawson Hagler, MSW, an independent, clinical polygraph examiner and owner/operator of Accountability Polygraph Services, Inc. in Englewood, Colorado. At the time we had just completed a case with Lawson, and Colleen interviewed him for an article she was writing for PI Magazine.

In this interview Lawson shared his knowledge and thoughts about the current practices and then-future trends in the polygraph examination field. Although this article is now a decade old, it still offers interesting insights into, as well as the history of, polygraph examinations. Lawson also compared polygraph examinations to voice stress testing and the Linguistic Statement Analysis Technique (LSAT).

We’re planning on seeing Lawson soon. We’ll ask him to give an update on this 2005 interview, which we’ll post later in Guns, Gams & Gumshoes.

Interview with Lawson Hagler, Polygraph Examiner

By Colleen Collins, All Rights Reserved

Colleen: For those of us who aren’t familiar, please tell us how a polygraph examination is performed.

Hagler: The examiner prepares relevant questions from a topic (ideally, one topic) that is significant to that interview. The examiner also uses standard questions, control and neutral questions, to get a baseline response. These questions are blended together.

A majority of our testing is done here at the office, where we seat the subject in a non-threatening room. We then place sensors on various locations on their body: galvanometers on the hand to detect changes in galvanic skin response (electrical activity and perspiration); a blood pressure cuff on the arm; and respiration monitors, called pneumographs, on the upper and lower chest.

Typically, 3 control questions are asked to obtain a baseline physiologic record. Ideally, 1 primary critical question is posed in 2 or 3 different phrasings. The subject’s responses to the relevant questions are then compared against responses to the control questions.

The premise is that someone is deceptive when they manifest abnormal physiologic responses, so the examiner poses questions and records the subject’s physiologic responses. In response to a neutral question, the blood pressure, respiration rate, and galvanic skin responses will show little variation. In response to a confrontational question, a deceptive or truthful answer pattern appears on a set of “charts” that are recorded on a computer or on long scrolls of graph paper. The charted results look similar to EKG paper and have marks that indicate when each question and answer was made in the session. Because multiple (“poly”) signals from the sensors record on a single strip of moving paper (“graph”), you get the term “polygraph.”

After the test, the examiner “grades” the charts at each juncture where a question was posed. Each set of physiologic responses is scored on a scale of +9 to -9. The +9 is an extremely non-deceptive answer (in fact, any score rated greater than +3 is scored non-deceptive). Similarly, deception is found at a score of -3 to -9. Any response between +3 to -3 is scored inconclusive.

Colleen: How long have polygraphs been around and how accurate are they?

Hagler: Polygraph instruments, similar to those still in use today, have been around for over 50 years. Computerization of this technology occurred in the early 1990s, resulting in significant improvements in overall test accuracy. If done according to established procedures, polygraph accuracy for single-issue (meaning, one relevant issue) exams is 90-95 percent. Of course, this is dependent on the integrity of the test process.

Colleen: What technological changes are on the horizon for polygraph examiners?

Hagler: There are software applications now available that assist in scoring the physiologic data obtained from clients. These algorithms ultimately will increase the accuracy of test outcomes. One such algorithm was developed by researchers in the Applied Physics Laboratory of Johns Hopkins University.

Also, new hardware technologies are now available. For instance, we know from extensive testing that pupil size varies considerably when a deceptive response is given, just as respiration rate, blood pressure, and skin response varies. A computer software and hardware package (developed by Limestone Technologies, Inc.) captures pupil response by means of a camera attached to the computer. As the computer is fed data from the traditional polygraph test, the web-cam device captures pupil size changes.

In addition my company has purchased motion sensors, embedded within a silicon pad on which the subject sits, that record body movements and other possible artifacts. This product, made by Lafayette Instrument ( uses piezo technology. Similarly, Limestone Technologies is currently developing a Sting Ray countermeasure cushion on which the subject sits while being administered the polygraph exam. This cushion records body movements aimed to offset some physiologic readings.

Private research groups and government agencies have reportedly begun analyzing data from a variety of additional measures, including EEG (ElectroEncephaloGraph or brain waves), skin temperature, and facial muscle movements.

In our office, we are also currently changing how we record and archive polygraph examinations. We have an entire storage area devoted to archiving old examination videos. Using digital technology, we are recording each examination to a DVD, which can be stored indefinitely and requires much less storage space. These DVDs then exist as evidence for court and can be used by other polygraph examiners to confirm the integrity of our examinations.

Colleen: Reports on voice stress tests claim they are not affected by drugs, alcohol, or manual manipulations unlike polygraph examinations. Also, that voice stress tests never have “inconclusive” results, which a polygraph sometimes has. Are you planning to incorporate voice stress tests into your polygraph exams?

Hagler: Although I’d like to believe the efficacy of voice stress analysis because they are less expensive, more portable, and require less training to use, they are also not yet proven to be a credible science. For example, no Department of Defense agency uses any form of voice stress analysis for investigative purposes. Considering detection of deception results can affect people for the rest of their lives, I prefer to use a scientifically validated technique over one that relies on selective personnel testimonials.

Colleen: What have you learned about Linguistic Statement Analysis Technique (LSAT is a process by which a trained analyst examines written or spoken language to determine truthfulness, deception, and other significant additional information) and is there a corroboration between LSAT and polygraph analysis?

Hagler: From what I have been able to gather about LSAT, the correlation is exciting. Both examine how a subject responds to a stimulus concerning a past event, and what response they produce when questioned about it. While LSAT approaches this from a grammatical reflection of what the subject experienced, the polygraph examiner employs a device to physiologically record potentially deceptive responses. In both cases, we are trying to ascertain the truth and to pierce a veil of deception. We both use different techniques to obtain an idea of what did or did not happen from that one person who frequently knows the truth. As a side note, this is why police will not publicize important details about crimes because often the person who is the object of interrogation will inadvertently supply that information either verbally, through the written word, or through physiologic responses. LSAT and a polygraph examination are both means of identifying that response, and both seek the truth.

Colleen: Thank you for your time, Lawson.

Hagler: I enjoyed it. Thank you.

All rights reserved by Colleen Collins and Shaun Kaufman. Any use of the content requires specific, written authority. Please do not copy/distribute images that are marked copyrighted or licensed—images in the public domain are yours to use.


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