Investigations: Polygraph Use
KeywordsDeception Lie detection Polygraph
The polygraph measures blood volume, breathing, pulse, and sweat rate of examinees to guide the polygraphist in determining truth and deception.
Since the inception of deception detection, physiological stress was always a problematic measurement. Heightened stress responses are often misinterpreted as deception because there is not a single distinctive stress response for deception. Unless this distinctive stress response exists or is identified, no machine would be able to detect lies, specifically the polygraph. When guided by the polygraph, the only capable lie detectors are the prepared polygraphists who carefully study their examinee’s physiological responses to control and relevant questions and attempts to beat the machine.
A Brief History on Truth and Deception
Deception started before our first language as humans and played a critical role in the personal gain and survival of many species. For example, anglerfishes use a shiny lure in the shape of a tasty juicy worm above their heads to attract other fish while hunting in the dark sea. Hognose snakes feign death and secrete a foul odor to warn predators that consumption of itself may lead to dangerous diseases, illnesses, or death (Owen 2015). Each example illustrates a different purpose of deception, with the anglerfish’s. method attracting others while the hognose snake’s method deterring others. We also use deception to attract or deter others, as we can also hang shiny tasty lures above our heads to attract others or secrete foul odors when threatened but that would probably produce mixed results. Regardless of our deception methods, we lie, trick, and deceive others out of fear, personal gain, or habit. “The ability to mislead or deceive probably carried an evolutionary advantage just as did fleetness of foot or the possession of an opposable thumb” (Lykken 1998). Since the birth of this evolutionary advantage, it is very likely that deception detection followed shortly afterward.
Before the recognized importance of deception detection, there was a magical and, at times, a religious belief that the honest would always emerge victorious and the deceptive would always be defeated. This belief existed in trails by combat, where the honest fighter was blessed based on their truthful character by a higher power and the deceptive fighter would be cursed, weakening them in combat and setting them up for defeat. The honest would also survive in trials by ordeal, such as walking on fire or dipping their arms in boiling water. The assumption was that under these trials, only the deceptive are punished and the truthful are protected (NTLS 2015).
The search for truth started as early as 300 B.C., where Bedouins of Arabia developed a hot metal spoon method where suspects of a crime were required to lick a hot metal spoon three times to determine if they were truthful or deceptive. This ritual was known as the “Bisha,” and the assumption behind this truth test was for persons who were deceptive would have a dry tongue and after licking the hot metal spoon would then have a burnt tongue. If the person was honest, their tongue would be moist and not dry, which would protect them from the hot spoon. Accused persons with a burnt tongue after this ritual would be found deceptive and guilty for the crime accused (NTLS 2015).
This salivary physiological response was common in other cultures as well and was also used in China, except the accused were required to chew rice instead of licking hot metal spoons. When the accused chewed and spat out the rice, rice that stayed on the accused’s tongue indicated deception. The assumption was that if the accused was innocent, their tongue would be wet and not dry because there was no reason to stress over the test if they were truthful (Leafloor 2014). Similarly, when we are under situations of high stress or deception today, one of our immediate physiological reactions is the dryness of throat, causing us to swallow as a response. Other physiological responses include increased breathing, pulse rate, and sweat, which of course led to other deception detection techniques.
African tribes used a smelling technique, where the accused stand around an African medicine man in a circle. The medicine man continuously smells the necks of the accused while delivering “blood-curdling” shouts along with another feverish smell of the accused (Trovillo 1939). These shouts heighten the stress levels of the accused, making them sweat uncontrollably and excessively. In this deception detection technique, it uses perspiration as the deception physiological response, and thus the person who sweats the most must be deceptive.
As you probably guessed, the aforementioned methods were not very reliable and often led to innocents punished for crimes they did not commit. Thankfully, modern-day deception detection techniques advanced beyond the use of hot spoons, rice, or a strong sense of smell. They start with nonverbal indicators, unique to each individual’s character and can range from rubbing or scratching the nose, eyes, ears, or the back of the head. Other indicators include grooming, heavy breathing, or cracking fingers. These nonverbal gestures are unique because they are learned through associations with others and start as early as childhood. However, these nonverbal indicators are not signs of deception; they are only signs of stress and are often misinterpreted as deception, similar to the techniques identified earlier. The distinction between stress and deception is assumed through our human behavior analysis skill, which is challenging to measure and accurately document. For starters, determining truth and deception depends on your own truthful or deceptive personal character and requires you to be well aware of your physiological stress responses. If you are truthful most of the time, you should search for truthful cues and if you are deceptive most of the time, you should search for deceptive cues. You can also be a truthful person and search for deception cues and vice versa but that might require extra practice. It might be easier for some of us to interpret verbal, nonverbal, and written forms of communication with the truthful or deceptive character and cues they are most familiar with – themselves or an intimate other. The act of measuring stress to assume deception is the function of the Lie Detector machine, also known as the polygraph.
The Genesis of Lie Detection Machines
The first prototype of the modern-day polygraph started with the analysis of blood flow within a deceptive person. In 1730, Daniel Defoe’s essay on prevention of street crime wrote how “Guilt carries fear always about with it; there is tremor in the blood of the thief” (Grubin and Madsen 2005). Defoe determined how unequal pulse changes and heart palpitations are strong indicators for deception during questioning which started in the early twentieth century with Austrian Benussi. Benussi’s research identified the relationship between blood pressure, pulse, and breathing rate now known as the Benussi ratio. Using the Benussi ratio, William Marston’s systolic blood pressure deception test became the prototype for the modern-day polygraph. Marston’s polygraph prototype used a standard blood pressure cuff and stethoscope while assuming the relationship between specific lie responses and changes in systolic blood pressure.
Marston’s prototype polygraph was submitted as evidence in the Supreme Court case Frye v. United States, 1923. Accused of robbery and murder, James Frye took Marston’s lie detector test and passed, which assumed Frye to be innocent. The trial judge refused to allow the admissibility of Marston’s apparatus as scientific evidence based on questionable validity from the scientific community and is now known as the Frye standard test. Since the use of Marston’s lie detection device in Frye v. United States, it attracted the attention of other professionals and eventually became the modern-day polygraph.
Larson created the first modern polygraph apparatus in 1921 that transcribed the physiological responses of blood pressure, pulse rate, and respiration (hence the name polygraph which means many writings). This first model of the polygraph proved successful and was later advanced to be portable by Leonarde Keeler, Larson’s disciple. Keeler furthered the portable polygraph and improved it to measure pulse rate, blood volume change, breathing, and sweat in 1939. Keeler’s model of the polygraph was the first lie detection instrument purchased by the Federal Bureau of Investigation and became the first prototype for the modern-day polygraph. Since the creation of the polygraph, professionals who were heavily involved in determining truth and deception merited its utility.
The polygraph records physiological responses of an examinee under stress. Under high levels of stress, which causes physiological responses to become more apparent, the sympathetic nervous system kicks in. The sympathetic nervous system is one of the two parts of our central nervous system and activates when we sense danger (also known as Walter Cannon’s fight/flight response) (Brown and Fee 2002). Over the years, Bradford’s fight/flight response was widely referenced and is now sometimes referred as “the four Fs” (fight, flight, freeze, and our popular and offensive four-letter word starting with an F and ending with a K). While experiencing one of the four Fs, the polygraphist determines truth and deception through interpreting polygraph charts and nonverbal behaviors during sympathetic stress. Some example of nonverbal behaviors include and are not limited to (a) pupil dilatation; (b) inhibition of salivary glands, waste elimination, and gastrointestinal tract; and (c) increased activity in breathing, sweat glands, and heart rates. These nonverbal behaviors could be deception indicators – some of which include “gaze aversion, increased or decreased movement, longer and more frequent pauses, a slower speech rate, hesitations, and speech errors” (Grubin and Madsen 2005). These categories of nonverbal behaviors are indicators of deception unique to each individual, thus requiring the polygraphist to study and determine baseline behaviors prior to assuming stress responses as deception.
So how does the polygraph measure physiological stress to assume deception? The modern-day polygraph measures breathing, heart rate, blood volume, and sweat with “(1) two expendable bands positioned around the thorax and the abdomen, measuring respiration, (2) two electrodes attached to the inside of the hand, measuring electrodermal activity, and (3) an inflatable cuff positioned around the upper arm registering blood pressure” (Meijer and Verschuere 2010). According to Bruno Verschuere, “skin conductance response is the most frequently applied and best validated measure for the detection of concealed information” (2010). Other scholars argue that breathing, heart rate, or blood volume to be stronger indicators of deception. Since there is no unique pattern or physiological response that would determine truth and deception, the polygraph is simply an instrument that records the physiological responses to guide a polygraphist in determining truth and deception.
Physiological readings are always accurate, but the challenge is proper interpretation of the readings (Aftergood 2000). The Supreme Court Case United States v. Scheffer in 1998 stated that “there is simply no way to know in a particular case whether a polygraph examiner’s conclusion is accurate, because certain doubts and uncertainties plague even the best polygraph exams.” According to Lykken, “We have already noted that for there to be an instrument that literally detects lying, there must be a specific lie response, a distinctive involuntary, bodily reaction that everyone produces when lying but never when telling the truth. There will never be a Truth Verifier (lie detector) until a specific lie response can be identified” (Lykken 1998). In short, since there is no specific lie response, no instrument will be able to detect lies.
Therefore, since the creation of the polygraph, there was an acknowledgment on how the polygraph is not a lie detector machine. There was also the growing concern that the polygraphist will be subject to bias and is not immune to uncontrollable factors that may alter their discretion in determining truth and deception. Nevertheless, the polygraph is still termed as the “lie detector test” with many researchers challenging the validity of its capabilities in determining truth and deception. The truth is that the polygraph does not determine truth and deception; it is the polygraphist conducting the exam with the aid of the polygraph and through the proper use and delivery of interview questions.
Phases of the Polygraph Exam
The polygraph exam is only successful if the polygraphist properly delivers each phase. Prior to the first phase (pretest), the examinee must be formally scheduled and given ample time in advance. This will allow truthful examinees to relax and calm down before the exam while heighten the stress of deceptive examinees. The first phase is the pretest interview and cannot be skipped or ignored at all costs. During the pretest interview, the polygraphist will introduce the examinee to the examination room and equipment, obtain informed consent for testing, and familiarize the examinee about the exam process, so there are no surprises throughout the exam. The polygraphist must be transparent and be very clear to the examinee about the process, the machine attachments, and recordings to ensure exam confidence. Lastly, the examinee must feel comfortable in the room, such as not feeling too hot or cold or have a need to use the restroom as any discomfort may distort polygraph chart results. This phase normally should take up to 20–30 min (Reid and Inbau 1977).
The polygraphist will demonstrate how the polygraph works through a mock test, where the examinee is instructed to tell a lie and the examiner will show that the polygraph has caught the lie and provide evidence of its accuracy. The polygraphist in this phase can also determine the examinee’s behavior, character, and truthfulness “based on the examinee’s demeanor and responses in the pretest interview and during the charting” (National Research Council 2003).
Depending on the type of interview, the polygraphist can also personalize the pretest interview by using psychometric techniques such as graphology, House-Tree-Person test, psychogeometry, the Thematic Apperception Test, and others to determine baseline behavior and establish rapport and theme. These psychometric techniques are not designed to determine truth or deception or to be a substitute to the polygraph. Psychometrics are used at the discretion of the polygraphist, which, if used incorrectly, may negatively affect the outcomes of the polygraph readings and interpretation. The purpose of the pretest interview is also to relieve an innocent examinee’s stress while heightening the sympathetic arousal of a guilty person. Therefore, the polygraph not only allows a polygraphist to determine an examinees physiological response and establish rapport but also indoctrinate the mind-set of the examinee that if they are innocent, they will be deemed innocent and if deceptive, they would be found guilty (Lewis and Cuppari 2009).
The pretest interview can also be an opportunity for the polygraphist to use other rapport-establishing techniques, such as Richard Bandler’s Neuro-Linguistic Programming (NLP). NLP has evolved over the years since its inception in the 1970s. The original purpose of NLP was to understand others better through studying eye movement gestures. Bandler categorized our five senses (sight, hear, smell, taste, and touch) into visual, auditory, and kinesthetic (smell, taste, and touch). Based on your eye direction when answering questions (top, middle, or bottom), you were a visual, auditory, or kinesthetic learner. Additionally, looking left or right while looking top, middle, or bottom would indicate truth or deception (Bandler et al. 1979). Regardless of the original intention of NLP, it is now employed as a method to establish theme in communication and in the pretest of the polygraph exam. There are many methods to establish theme, but one of the easiest methods is to determine what type of learner an examinee is and to use the words associated with the learning method. For example, if the polygraphist finds their examinee to be a visual learner, they would use visual-oriented words such as “I see what you mean.” If the examinee is an auditory learner, the polygraphist would use auditory-oriented words such as “sounds good.” Lastly, if the examinee is a kinesthetic learner, the polygraphist would use kinesthetic words such as “smells fishy” or “feeling salty.” This technique as with many other psychoanalysis techniques is a pseudoscience and is not always scientifically proven to work. Regardless, if it actually works or not, these techniques would boost the polygraphist’s confidence in determining truth and deception. It is this immeasurable confidence that drives the polygraphist to hold their breath longer than the examinee, to separate and exhaust deceptive examinees from the truthful. In short, this NLP rapport technique is one of the many theme techniques professionals can use to establish rapport and can be used in the pretest phase of the polygraph exam.
In the in-test phase, the polygraphist must communicate every question clearly and carefully as shared in the pretest phase. Polygraph exam questions cannot be ambiguous or use sensitive words related to the crime. For example, in a child molestation case, the polygraphist should not use the word “rape” or “pedophile” but instead use terms such as “inappropriately touch” or “sexual intercourse.” The polygraphist should also not use technical jargon that the examinee would not understand such as fellatio, as it would lead to confusion and inaccurate polygraph writings. Questions should also not be lengthy as it would dampen the stress levels of deceptive examinees and stress out honest examinees.
Three important types of questions asked during the in-test phase are control, relevant, and irrelevant. Before the test begins, the polygraphist will read their list of questions to the examinee in any order to ensure they understand each question. This list of questions will have a mix of control, relevant, and irrelevant questions. The sequential order of control, relevant, and irrelevant questions is extremely important and changes based on the type of interview. There are many standardized test orders, some of which also have additional instructions. For example, by assigning two relevant questions one after another and asking the examinee to answer truthfully to one and deceptively to another is known as the positive control test. By asking examinees to deceptively answer every control question is known as the directed lie test. Regardless of the question set, the polygraphist will inform the examinee that only the questions read to them will be asked and that there are no surprise questions. The most well-known polygraph question set is the control question test, which focuses on physiological responses to control and relevant questions.
Control questions are vague questions that cover events from previous life experiences and are recommended to be related to the crime accused. Control questions are meant to make the subject uncomfortable because the questions are designed to make it difficult for the examinee to answer “no.” For example, in a crime related to robbery, the examinee would be asked, “in your entire life, have you ever stole something?” For most of us, we take things from time to time and would not classify the action as stealing. For example “borrowing” scissors or other office supplies from our colleagues and “forgetting” to return it. Although the intention to steal was never there, the action of taking other peoples’ possession without permission can be labeled as stealing for some and not for others. For individuals who would label this action as stealing, they would experience physiological stress when confronted with this control question. “Control questions are designed to provide the innocent suspect the opportunity to become more concerned about questions other than the relevant questions and to produce stronger physiological reactions to control questions. If the subject shows stronger physiological reactions to the control as compared to the relevant question, the test outcome is interpreted as truthful. Stronger reactions to the relevant questions indicate deception” (Lykken 1998).
Relevant questions are questions that are directly related to the crime at hand. If the suspect has committed more than one crime, the crime that is the most serious will stress them out the most, providing the strongest physiological response. For example, if the suspect was involved in three different drug-related crimes and one out of the three involved murder, the murder case is most likely going to occupy the suspect’s concentration, focus, and effort in concealing deception. The other two drug-related crimes would be the least concern to the suspect and produce lower stress responses. This is known as the anti-dampening concept and is defined by Lykken as “a person’s fear, anxieties and apprehensions are channeled toward the situation which holds greatest immediate threat to his self-preservation or general well-being, (and that there is) an ability within us to tune in that which way indicate trouble or danger by having our sense organs and attention set for a particular stimulus and oriented in a manner that will dampen any stimulus of lesser importance” (1998). For example, if a respectful law-abiding student is taking a polygraph exam for a job opportunity in the federal government and were previously engaged in “agriculture,” questions related to experimenting with cannabis would heighten the student’s responses knowing that it would disqualify them from job employment. Questions related to murder or stealing would not generate strong physiological responses because the student’s entire focus is on their past cannabis experiences. In sum, the anti-dampening concept will affect responses to relevant questions depending on the situation, examinee’s concentration, and focus.
Irrelevant questions are questions that are completely irrelevant to the crime under investigation. Sample irrelevant questions are “Is your name Phil?”, “Did you ever ride a bike?”, and “Are you in New York right now?” “The primary purpose of the irrelevant questions is to ascertain the subject’s normal reactions – his ‘norm’ – under test conditions” (Reid and Inbau 1977). The normal reactions are important because it is also the examinee’s baseline behavior. Although irrelevant questions help the polygraphist establish the norm behavior of their examinee, the problem is that if the examinee lies on the irrelevant questions and they are not confronted on the lie, the examinee will believe they can evade detection when confronted with relevant questions. As stated earlier, depending on which set of questions produces higher levels of physiological response, the subject will be deemed truthful or deceptive. If the subject shows higher physiological responses to the control questions, they are deemed truthful. If the subject shows higher physiological responses to the relevant questions, they are deemed deceptive. The actions taken by the examinee to alter their physiological responses to control and relevant questions to misguide the polygraphist is known as “beat the machine.”
Beat the Machine
“Beat the machine” is defined as the examinee’s attempt to manipulate the results of polygraph readings through hidden methods undisclosed to the polygraphist. An estimate of 20% of examinees often try to “beat the machine” through various methods such as voluntary muscular movements to mislead the polygraphist during questioning (Reid 1945). These muscle contractions are also known as peripheral resistance, where based on muscular activity, the resistance of blood flow increases or decreases. Reid’s research shows that these voluntary unobserved muscular movements have the following properties: (a) all typical blood pressure responses can be produced voluntarily and at will, (b) voluntary and at-will blood pressure responses can be differentiated from true indications of guilt, and (c) recorded evidence of muscular evidence is an indicator of deception (1945). In short, unobserved muscular movements during polygraph tests are methods to beat the machine, specifically when asked control questions.
The best advice to beat the machine is to identify the control questions and to alter your physiological reaction to the control questions. This action will make it difficult for the polygraphist to differentiate between control and relevant question physiological responses. A method to alter your physiological reaction is through self-inflicted pain or tightening your muscles to control physiological responses. If you are unsure of how to identify the control questions to beat the machine, you can also relax, hold your breath, or do anything to calm yourself when you are asked the relevant questions. Any method that would cause the polygraph charts to show similar physiological responses to control and relevant questions will allow you to beat the machine successfully. Being mindful of methods to beat the machine will help subjects pass the polygraph test, as “a high proportion of honest people will fail lie detector or honesty tests when they rely on their truthful answers to demonstrate their innocence or good character. Meanwhile, the more clever of the villains will employ countermeasures to ensure that they manage to pass” (Lykken 1998).
After the in-test phase is the posttest phase, where the polygraphist will have the results of the exam immediately after the in-test phase. The polygraphist will determine the examinee as deceptive, honest, or inconclusive. Deceptive is determined by the examinee showing consistent and stronger physiological responses to relevant questions. Honest is determined by the examinee showing consistent and stronger responses to control questions. Inconclusive is when the polygraphist is unable to determine if the examinee is deceptive or honest. Deceptive and honest exam results are determined by a numerical scoring system, traditionally scoring deceptive responses as negative points and honest responses as positive points (Synnott et al. 2015).
Measuring Polygraph Validity
Measuring polygraph validity is extremely challenging and if not, more confusing and complicated given the required learning curve of accurately interpreting and transcribing polygraph charts during testing. Although assumingly used for determining truth and deception, the polygraph is only an instrument that would guide the polygraphist in reassuring their discretion. Empirical studies show that “in experimental settings, the ability of the average person to catch a liar is rarely above 60%” (Grubin and Madsen 2005). Additionally, the United States Justice Paul Stevens determined the polygraph only having an 85% to 90% accuracy reliability rate with critics estimating a 70% accuracy rate (Gershman 1998). Given the percentages here, it appears that the lie detection rate between an average person and the use of a polygraph can be up to 25% when using the polygraph. Do not let these percentages fool you, as “the clinical judgment of a polygraph examiner is no more valid than that of any other observer, just as subject to bias and prejudice, and probably wrong nearly 50% of the time” (Lykken 1998). Empirical research on lie detector accuracy rates and its percentages are best explained by Benjamin Disraeli’s quote “There are three kinds of lies; lies, damn lies, and statistics.”
Testing Polygraph in Laboratories
Critics who attempt to debunk the validity of the polygraph often test its legitimacy through controlled laboratory settings. Laboratory experiments on measuring polygraph validity often produce misleading results given the nature of the experiment. Laboratory settings offer a completely different environment and experience to examinees compared to real-life polygraph exams. “Laboratory studies that are based on nonemotional orienting responses absolutely fail to replicate the field conditions that elicit emotional defensive responses wherein both the guilty and innocent examinee’s primary emotion is ‘fear’ of the consequences if found deceptive which in criminal cases could result in imprisonment” (Matte 2011).
Other polygraphists drew the same conclusions regarding polygraph laboratory studies. Lykken believed that laboratory studies “have serious disadvantages for predicting lie detector accuracy in real-life criminal investigations” (Lykken 1998). The first disadvantage is that volunteers do not accurately represent criminals in real life and, thus, will not express or experience real concerns to the lies they are instructed to tell. The second disadvantage is that there are no perceivable consequences for volunteers if they fail the polygraph exam. The third disadvantage is that laboratory polygraph mock studies occur shortly after a mock crime occurs. This does not happen in the real world, where polygraph testing may occur days or even weeks after a crime occurs. Therefore, we can conclude that laboratory tests cannot determine polygraph validity.
Employee Polygraph Protection Act of 1988
According to The Employee Polygraph Protection Act of 1988, all private employees are protected from an employee requirement to take the polygraph exam. Employers cannot request or even suggest employee candidates to take the polygraph exam, nor are they allowed to terminate an existing employee because of a refusal to take a polygraph exam. The Employee Polygraph Protection Act of 1988 does not apply to federal, state, or local government agencies, nor does it apply to professions regarding national defense.
Currently, the polygraph is used to screen applicants for government positions and is known as the applicant screening test. The polygraphist follows the same process as they would normally and work off multiple question lists. The examinee is tested to see if their physiological responses remain constant across all content areas, from drugs to violence to stealing and other acts that would disqualify them for employment. Any content area that draws stronger physiological responses will be asked repeatedly with longer pauses to determine deception. If the polygraphist is convinced the examinee is deceptive, they can stop the polygraph and directly confront them about their deception. If the examinee continues to deny deception, the polygraphist will continue with the test and return to the sensitive content area later. As you probably guessed, many examinees also try to beat the machine. The most important fact to remember in preparation for the polygraph exam is your belief in the machine. “Once you believe in the machine, it works. Once you believe in the charts, it works. The polygraph does not believe in you, but you will believe the polygraph” (Lykken 1998).
Although known as the lie detector machine, the polygraph would only serve as a guide for the polygraphist to determine truth and deception as a Microsoft PowerPoint presentation would serve as a guide for a presenter. It is not the flashy graphics or song cues in a PowerPoint presentation file that makes the presentation or lecture a living masterpiece – it is the presenter himself or herself. As for the polygraph, it is not its physiology measurement capabilities, it is the polygraphist himself or herself. The polygraph only appears to be the better lie detector because of its scientific presence and physiology recording function. When we combine the polygraph presence with our naïve dependency on technology, we believe in the machine. It is true about the polygraph that it is close to perfect in measuring physiological response, but it still requires a person to use their discretion to determine truth and deception given the unique character and nature of each individual person.
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