Polygraph testing: truth or dare

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October 2008 Security Services & Risk Management

Compiled by CGC researcher, Elize Buys, from a presentation by Sarel Badenhorst on behalf of SAPPA

The polygraph, it has been claimed, is able to indicate whether someone is telling the truth with a high degree of accuracy. This article aims to take a closer look at the polygraph’s claim to fame.

A polygraph is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration and skin conductivity while the subject is asked and answers a series of questions, on the basis that false answers will produce distinctive measurements. The polygraph measures physiological changes caused by the sympathetic nervous system during questioning (Wikipedia, 2008).

Most humans have five senses from which messages are sent to the brain. If any threatening message is received by the brain via any of these senses, the autonomic nervous system activates a defence mode for the human to protect itself. This is also known as the fight or flight syndrome. This causes some physiological changes to take place in the human body such as a faster heart rate, changes in blood pressure; they will inhale additional oxygen and there will be an increase in sweat gland activity.

The same changes will take place in any circumstance where a human experiences a threat and makes a decision what to do in order to attempt to protect him/herself. When a person is asked a question, about a crime or activity, of which he is well aware via his memory that he is guilty, a fight or flight syndrome response could be activated to tell a lie in order to protect him/herself. If the question did not threaten the person, the necessity to lie would not have been an option as an innocent person would have simply told the truth. The strong focus of the human being is to survive and therefore the fear of being caught out lying threatens your immediate well-being.

The function of the polygraph instrument is to make use of physiological responses visible for analysing. The polygraph instrument records four major responses:

1. Thoratic respiration (chest).

2. Abdominal respiration (stomach).

3. Electro dermal activity (sweating).

4. Cardio vascular responses (relative blood pressure).

The innocent person will naturally always be tense, because of the unfamiliar circumstances he finds himself in. The fact that he is being investigated, that he does not know the polygraphist, that he does not know how capable the polygraphist is and the fact that he does not know how the polygraph works all contribute to nervousness. Therefore the innocent person's physiological responses will be greater than normal, but will stay on equilibrium. This condition is also referred to as general nervous tension. The innocent person will not show significant and consistent physiological changes towards the relevant (target) questions on the test. The guilty person will focus all his attention to the questions on which he has fear of detection of deception. This will cause the fight or flight syndrome, which will cause significant and consistent physiological changes towards the target questions.

The history of polygraph testing

The idea that lying causes physical side-effects has long been claimed. In West Africa persons suspected of a crime were made to pass a bird's egg to one another. If a person broke the egg, he or she was considered guilty, based on the idea that their nervousness was to blame. In ancient China the suspect held a handful of rice in his or her mouth during a prosecutor's speech. Since salivation was believed to cease at times of emotional anxiety, the person was considered guilty if by the end of that speech the rice was dry (Wikipedia, 2008).

Early devices for lie detection during police investigations include an 1885 invention Cesar Lombroso used to measure changes in blood pressure, a 1914 device by Vittorio Benussi used to measure breathing, and an abandoned project by American William Marston which used blood pressure and galvanic skin response to examine German prisoners of war. Marston was the self proclaimed 'father of the polygraph' despite his predecessor's contributions. Marston remained the device's primary advocate, lobbying for its use in the courts. In 1938 he published a book, 'The Lie Detector Test', wherein he documented the theory and use of the device. In 1938 he appeared in an advertisement by the Gillette Company claiming that the polygraph showed Gillette razors were better than the competition (Wikipedia, 2008).

How is polygraph testing conducted today?

There are typically three phases: a pre-test, an in-test and a post-test phase, which includes the scrutiny of the recorded test data and analysis. Some believe that the process takes 30 minutes to complete, yet the whole process should take up to 90 minutes. The process follows the following steps:

Pre-test phase: the procedure will be discussed and the examiner will carefully review the questions to be asked in relation to the specific issues being addressed. Sometimes the sensors are attached so as to perform a 'stimulation test' (Polygraph Testing, 2008).

In-test phase: During the in-test phase the actual charts are recorded. This starts with the examinee being attached to the polygraph, and then asked the previously discussed questions in a 'yes' and 'no' fashion. The data is collected by the sensors and recorded electronically (Polygraph Testing, 2008).

Post-test phase: In this phase the polygraph examiner will analyse the data on the chart recordings and give an opinion as the truthfulness or honesty of the examinee. An opportunity to explain the physiological reactions in relation to the questions will normally be given to the examinee (Polygraph Testing, 2008).

How accurate is the polygraph?

There are many research studies available on the accuracy of the polygraph examination. Based on the studies now available, experts assess the accuracy of polygraph examinations administered by a competent examiner to be about 90%. Level of skill and experience of the examiner plays an important part in the accuracy of the examination. Comparative studies have shown that polygraph examinations yield an accuracy that equals or exceeds that of many other forms of evidence. In one study, it was shown that polygraph examination produced an accuracy that was comparable to results obtained by document examiners and fingerprint analysts, and exceeded that of eyewitnesses (FAQs about the polygraph, 2001).

The polygraph is often wrongly portrayed as a 'lie detector'. What the polygraph does is it records changes in the subject's stress level as manifested in his or her respiration, galvanic skin resistance and cardiovascular activity when asked a series of test questions comprising control, relevant and baseline questions. The polygraph does not detect lies. In fact, its function is very similar to that of an X-ray machine - it does not detect illnesses.

The polygraph examiner carefully studies all available case data and physiological data collected and makes an assessment of the subject's truthfulness, deception or an inconclusive result. The process is highly complex and the accuracy of the result is dependent on the skill and experience of the examiner. The process is quite similar to how a doctor or surgeon makes a medical diagnosis. Hence it is flawed to generalise and say whether the polygraph is reliable or unreliable. Rather, it should be whether the particular polygraph examiner carrying out the test is reliable or unreliable (FAQs about the polygraph, 2001).

The situation in South Africa

An increasing number of companies have been making use of the polygraph as a regular feature of the work environment. The polygraph has been adopted by South African companies as well as the South African Police Service, and polygraph testing of deception was endorsed by the former SAPS commissioner George Fivaz in 1997 (Polygraph-Based Testing of Deception and Truthfulness, 2008).

The South African Professional Polygraph Association (SAPPA) is a professional organisation that promotes quality polygraph services to the society, to lead in the regulation and conduct of the profession. SAPPA subscribes to the ethical, technical and moral standards of the World Polygraph Body, the American Polygraph Association (SAPPA, 2008).

Supporting views to polygraph testing

Polygraph testing has many uses and do, according to those who use it, add value. Some of its uses include:

Random Test: This is where the honesty of a person is verified whilst working at a specific place.

Pre-employment Test: This is a test conducted on a potential, future employee, to verify his honesty on his application prior to employment.

Specific Test: This is an investigation test used to identify a suspect and also to eliminate innocent people from a list on a specific crime.

As a tool to investigation

According to William J. Warner, time and again, the debate over the use of polygraph testing centres around its reliability and validity (or lack thereof) with little discussion from either side as to its utilitarian component. According to him this is a common oversight neglected in the literature and ignored by those seeking to criticise an investigative technique because it is not always reliable. However, law enforcement investigators who have a commitment to the public they serve recognise the polygraph's usefulness as a tool for obtaining information not previously known in criminal investigations.

He refers to a study in 1996 of 96 child support cases listed as questionable due to the unknown whereabouts of the father; the researchers informed the mothers that they would use the polygraph to verify the unknown status of the fathers. Following the mere suggestion of polygraph testing, 51 of the mothers came forward with additional information, resulting in the resolution of those cases. Additionally, in 2002, three men confessed to murders following their polygraph tests. During a polygraph pre-test, one man confessed to child molestation. When another man was notified that his polygraph had been scheduled, he confessed to shooting his wife. And, after failing a polygraph test, a third confessed to killing his wife (Polygraph Testing - A Utilitarian Tool, 2005).

Criticism to polygraph testing

There exist some criticisms toward polygraph testing; some of the arguments will be discussed under this heading.

Lack of training and continuous education: The accuracy of a polygraph test could be influenced when conducted by an untrained or inexperienced polygraphist. The following problems might occur:

* Incorrect formulation of questions.

* Incorrect use of polygraph techniques.

* Incorrect preparation of examinee.

* Incorrect evaluation of charts.

* Facts on brief influencing the polygraphist to doubt the result.

* A good impression of the examinee could cause doubt to the result.

Subjectivity involved during polygraph testing: A polygraph examination involves a lengthy pre-test interview during which the examiner gains access to a wealth of background information and formulates specific questions that are then used during the test phase, when physiological responses are recorded. The type of questions that are constructed and the interpersonal manner with which they are posed can have a significant influence on the examinee's physiological responses. Moreover, the scoring and interpretation of the polygraph chart also require subjective judgments that can be influenced by an examiner's preconceptions, and there remains a critical need for well-validated computerised scoring and interpretive systems (Exploring controversies, 2008). An exposé on private polygraph firms aired by 60 Minutes in 1986 underscores the subjectivity of the process and its susceptibility to confirmation bias due to the contamination of an examiner's diagnosis with information obtained outside of the formal polygraph test. As summarised by Ben-Shakhar (1991, 236):

Three different polygraph firms were independently called to test an alleged theft of a camera and lens from a photography magazine office employing four employees. In fact, nothing was stolen from the office, but the polygraph examiners were told that it could only have been done by one of the four employees. Each polygraph examiner was told that 'it might have been -,' with a different employee being fingered in each case (a decidedly weak fingering). In each case, the polygraph examiner identified the 'fingered' employee as deceptive, and cleared the other 'suspects'. Moreover, all polygraph examiners expressed complete confidence in their decisions. This demonstrates not only that polygraph examiners can go wrong, but that their judgment and decision-making processes are infected by a systematic and powerful source of bias, a bias caused by contamination. (Exploring controversies, 2008).

Uses and types of polygraph tests

Broadly speaking, polygraph tests are used for two primary purposes: in investigating specific incidents (eg, crimes, security violations) and for screening (eg, evaluating the honesty of prospective or current employees). Although there are subtle variations, two primary types of polygraph tests are used: the control question test and the guilty knowledge test (Exploring controversies, 2008).

The rationale underlying the interpretation of a CQT is that guilty individuals will be more aroused by the relevant than the control items, whereas innocent individuals will be more aroused by the control than the relevant items. Because the relevant and control questions are discussed and agreed upon by the examiner and examinee during the pre-test interview, they are easily distinguished during the test phase. This has two consequences, both of which tend to undermine the validity of the CQT.

First, both innocent and guilty suspects recognise which questions are important for their futures, and are likely to feel considerably more threatened by the relevant questions. Many studies of the CQT reveal a high rate of false-positive diagnoses of deception. It is not uncommon for 40% to 50% of innocent suspects to fail a CQT polygraph examination (Lykken 1998; NRC 2003). Second, whether innocent or guilty, some examinees can take advantage of any number of countermeasures to systematically increase their physiological responses to the control questions, thereby passing the test. Lykken (1998) notes that laboratory studies have shown that college students can be trained to beat this type of polygraph test in under an hour (Exploring controversies in the art and science of polygraph testing, 2008).

The GKT (guilty knowledge test) has been developed by scientists and holds much greater promise for the investigation of specific incidents. Rather than attempting to determine the truthfulness of an examinee's responses to relevant items, this technique aims to assess whether an examinee possesses knowledge to which only a guilty individual would have access. To do so, a series of multiple-choice questions is constructed such that one choice is correct and the others are equally plausible to an innocent suspect.

For example, one item relevant to a murder investigation could include a number of potential murder weapons; another could include descriptions of the victim's clothing at the time of the attack, and so forth. A total of six choices are usually provided for each question, with the correct alternative positioned randomly among the latter five choices (due to primacy effects, the first choice is not scored). The examinee is asked to repeat each of these choices out loud, which may serve to thwart potential countermeasures based on self-induced competing thoughts, and a score is calculated based on the frequency with which the maximal physiological response coincides with the correct alternative. An examinee who consistently responds most strongly to the correct choices is judged to possess knowledge of the incriminating information, whereas an examinee who responds to the correct choices at chance levels is judged not to possess this knowledge (Exploring controversies, 2008).

The rationale underlying the GKT is based on the well-established nature of an 'orienting response'. This is similar to the so-called 'cocktail party effect' whereby one's attention is automatically drawn to familiar information, such as hearing your own name spoken at a crowded cocktail party. It is especially difficult to suppress such a response to familiarity, and it would be difficult to systematically increase one's physiological response to all of the incorrect alternatives. To do so would require a large number of self-induced increases and decreases in arousal. This would be difficult to effect repeatedly and would lead to two additional problems. First, employing countermeasures a great many times may tip off a skilled examiner, thereby signalling the intention to deceive. Second, it may be possible to detect statistical differences in physiological responding if the smallest response consistently coincides with the correct alternative or if far fewer maximal responses coincide with the correct alternatives than would be expected by chance. In other words, the successful use of countermeasures requires that one establish a genuinely chance-level pattern of responding, which would be exceedingly difficult (Exploring controversies, 2008).

The legality of polygraph testing

There are three very important requirements of the CCMA regarding polygraph evidence to take note of. Firstly, an examinee must sign consent that he freely and voluntarily agrees to take the polygraph test. Without the examinee's consent, any information gained from the test may be considered forced. Secondly, the polygraph test can not be used as the sole evidence in any given case. Polygraph testing can only be supportive evidence, due to the controversy surrounding the issue. Lastly the CCMA looks at the training and experience of the polygraphist. Therefore, it is in the interested party's best interest to hire a qualified polygraphist that does qualify according to SAPPA and APA standards.

Polygraph testing assumptions is based on valid/scientific beliefs, it is true that when a person feels threatened he/she reacts with the fight or flight syndrome. It is also true that this reaction causes certain physiological responses, such as blood pressure, pulse, respiration and skin conductivity. What is questioned however is the validity of the process, especially if in some cases a person can be trained within an hour to pass the test? The question remains: can polygraph testing results be seen as true beyond reasonable doubt? This question remains to be answered by every company considering using polygraph testing. It is in the end each individual company's own choice.

Reference list

Wikipedia, 2008.

http://en.wikipedia/wiki/Polygraph

Accessed on 2008/05/12

Polygraph Testing, 2008.

http://www.forensic-centre.com/assessments/lie-detection

Accessed on 2008/05/14

SAPPA, South African Professional Polygraph Association, 2008.

http://www.polygraph.org.za

Accessed on 2008/05/14

Polygraph-Based Testing of Deception and Truthfulness: An Evaluation and Commentary, 2000.

http://web.uct.ac.za/depts/psychology/plato/poly.pdf