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The Polygraph: The Truth about Lie Detectors


  • Introduction
  • Major reason for using the polygraph
  • Measures of the polygraph
  • Benefits of using the polygraph
  • Misuse of the polygraph
  • Countermeasures to the polygraph
  • Ethical issues and the polygraph
  • Conclusion
  • References


Polygraph is one of the most successful inventions because a lie detector can help consistently in the investigation of crime, in the process of interrogation and when the truthfulness of an individual has to be measured. However, the application of polygraphs and their reliability is still under a question. In fact, there are many proponents, who believe that polygraphs are very effective and can help to find out whether a person undergoing polygraph test is telling the truth or lies. On the other hand, there are many opponents, who believe that not a single machine can define whether a person is telling the truth or lies. In such a situation, many researches dedicated to the problem of the study of polygraph fail to reveal whether polygraph is really reliable and accurate or probably it can be misused and fail to provide accurate and adequate results. In such a situation, the question concerning the scope of the application of polygraphs arises. Polygraphs were introduced as tool used for the investigation and interrogation. At first, they were used by law enforcement agencies, and later they were used by other organizations, in the course of recruitment, for instance. At the same time, the use of polygraphs in the criminal justice system is still uncertain and courts normally reject the use of polygraphs because of uncertainty of the results of the use of polygraphs and their reliability. On the other hand, under normal conditions an individual undergoing polygraph test cannot deceive it, if he/she does not intend to deceive the machine. However, individuals, who are willing to deceive it, do have a chance but still there is a possibility that they fail. Therefore, it is obvious that today polygraphs are imperfect but it does not necessarily mean that polygraphs should be totally rejected because they need further technical improvements to make them more reliable, although their use should be strictly regulated by legislations to protect privacy and other rights and liberties of individuals.


Historically, polygraphs were introduced as lie detectors that helped to identify whether a person undergoing polygraph test is telling the truth or lie. In this regard, polygraphs were used by law enforcement agencies in interrogations of suspects. However, steadily the scope of use of polygraphs expanded as well as reasons for their use. For instance, many organizations have started to use polygraphs for recruitment of their employees, while many state agencies, including law enforcement agencies use polygraphs for recruitment of employees and their promotion as well as to test them to find out whether they still can perform their duties. For instance, CIA conducts polygraph testing of its employees to identify spies or individuals that are inclined to lie, which are apparently dangerous for CIA because they are not reliable for the agency.

At the same time, one of the major reasons for using polygraphs is the prevention of corruption, especially in government agencies, law enforcement agencies, and public organizations. Basically, the problem of corruption is very serious and the difficulties begin with the definition of this phenomenon and the lack of actual opportunities to prove cases of corruption. What is meat here is the fact that corruption may take place but it does not necessarily mean that cases of corruption may be legally proved and, consequently, punished or prevented. In actuality, the schemes of corruption may be extremely complicated, especially on the high level. As a result, the problem of providing sufficient evidence and proofs of the fact of corruption is one of the major obstacles on the way to law enforcement and prevention of corruption.

In order to better understand the extent of this problem, it is extremely important to define clearly the concept of corruption. In this respect, it is possible to refer to the definition of corruption give in accordance to the Police’s Patrol Guide, which states that corruption and serious misconduct are defined as “criminal activity or serious misconduct of any kind, including the use of excessive force or perjury that is committed by a member of the service whether on or off the duty” (Bouza, 232). Obviously, such a definition may interpret various actions as corruptive or as serious misconduct. On the other hand, it is also evident that such a definition may be characterized as lacking more concrete statements.

In fact, it is necessary to understand that corruption is quite a complicated phenomenon and, as a rule, it involves the use of the position of a member of the service, his/her access to information related directly or indirectly to criminal cases and the ability to use this position or knowledge for criminal purposes. Also, it is worthy of mention that corruption actually implies the integration of the criminal underworld and police since corruption naturally leads to the violation of laws by police officers. Consequently, if police officers start to violate existing laws and use their position in their own interests than they become a part of the criminal underworld. Moreover, often corruption implies the direct interaction between the criminal underworld and police officers.

At this point, it is possible to speak about two types of corruption of police officers. First of all, it is possible to speak about the use of the position and the authority of police officers in their interests without any external influences. For instance, it is possible to mention that there were some cases in the history of the Policewhen police officers simply racketeered citizens, in order to get some money or any other kind of reward either for “protection” or ignoring the presumable violation of laws. It should be said that such situations do not necessarily imply that citizens do really violate laws, but the allegations may be simply fancied by police officers and through terrorizing of the citizens they can force either to pay money, give reward, or service, etc. Obviously, such actions should be qualified as corruptive since they lead to the violation of laws, including the use of excessive force, by members of the service in accordance with the norm of the Police’s Patrol Guide.

On the other hand, it is possible to speak about another type of corruption which is not less, or, probably, even more serious than the one that has been just discussed above. This type of corruption may be qualified as the close interaction between police officers and the criminal underworld. In practice, this means that police officers interact with the criminal world and serve to the interests of the latter. Obviously, such a situation is extremely dangerous since it threatens to the normal work of police. It proves beyond a doubt that the corruption of police through its interaction with the criminal underworld. In such a situation, police simply becomes a part of the criminal underworld since police officers who interact with the latter do not serve to the interests of society.

Naturally, the necessity of the struggle against corruption is extremely significant. It should be said that corruption in all spheres is dangerous, but, in relation to police, corruption is particularly dangerous. In fact, police, as the major law enforcement agency, is the basis of the preservation and maintenance of the existing laws and social order. This is why, when police gets corrupted, then the entire society, the existing social order starts to destruct gradually. In actuality, the problem of corruption should be viewed as a serious social problem and not just a problem of police, or more specifically, the Police. As a result, the prevention of this problem in police is particularly important because police, which does not face the problem of corruption, could guarantee the observance of laws and legal norms which are basic for the social stability and protect basic human rights and democratic values.

Obviously, the recent cases concerning corruption, perfectly illustrate the extent to which this problem is deep-rooted within the Police. In this respect, it is worthy of mention that from the cases discussed above it is obvious that it is only inexperienced or low-qualified police officers that are involved in corruption-related cases. In stark contrast, there are veterans that involved in such cases and it is very important that they are punished even after their retirement. This fact proves that corruption is totally unacceptable, especially within the Police.

At the same time, the involvement of veterans may be viewed as evidence of the fact that the problem of corruption is really widely spread in the police and, what is probably even more important, it is also evidence of the fact that this problem has not died out yet, instead, it is still relevant that makes its solution particularly important.

On the other hand, a logical question arises: why the cases that date back to 1970s and 1980s such as the case of Caracappa and Epolito are investigated only recently. In this respect, it should be said that such cases reveal the fact that the struggle against corruption within the police became more effective than it used to be in the past, even a decade ago. This means that nowadays investigators have less obstacles on their way of revealing crimes of police officers working in the Police.

In such a situation, it is necessary to underline that the recent successes are basically the result of profound changes initiated in the early 1990s when the anti-corruption law enforcement units were consistently reconstructed or even created to cope with the problem of corruption. For instance, in 1992, the Mollen Commission, officially called as the Commission to Investigate Allegations of Police Corruption and the Anti-Corruption Procedures of the Police Department, was created by Executive Order of Mayor David Drinkins to “investigate the nature and extent of corruption in the Department; to evaluate the Department’s procedures for preventing and detection corruption; and to recommend changes and improvements in those procedures” (Lindsay, 74).

On the other hand, it should be said that the creation of such commissions targeting the investigation and prevention of corruption within the police is not a new idea. In fact, there were similar commissions created in the past which are still working. For instance, it is possible to name the Knapp Commission, officially named the Commission to Investigate Allegations of Police Corruption and the City’s Anti-Corruption Procedures, which was established in 1970 and investigated widespread institutional corruption in the police after Frank Serpico and other police revealed a citywide network of rogue cops (Lindsay, 78).

However, probably the most important anti-corruption unit is the Police’s Internal Affaires Bureau (IAB), which is charged by the Police Commissioner with the “institutional accountability, implementation and maintenance of the Department’s anti-corruption programs” and basically it targets the investigation of serious misconduct and allegations of corruption (CCPC Report: Internal Affairs Bureau Recruitment and Retention, 4). In general, the major goal of the IAB is defined as the provision of “effective corruption control through analyzing allegations and trends, and conducting comprehensive investigations designed to ensure the highest standards of integrity” (CCPC Report: Internal Affairs Bureau Recruitment and Retention, 5). All these commissions and IAB target the prevention of corruption and investigation of illegal conduct of police officers that naturally decrease the threat of the further spread of corruption within the police.

At the same time, along with the prevention of corruption polygraph tests are still very important in other fields, although the use of polygraphs in the criminal justice system, for instance, raises heat debates because many specialists (White, 2001) believe polygraphs to be unreliable, whereas others (Lewis & Couppari, 2009) believe that polygraphs are effective tools which can help to identify lie. In addition, many organizations attempt to use polygraphs to test their employees but such use of polygraphs, especially by private organizations, raise a number of legal and ethical issues.


The polygraph, as refined by Marston in the 1920’s and still used today, measures three physiological responses: (1) depth of respiration, gauged by pneumatic tubes strapped around the chest and abdomen; (2) cardiovascular activity, by a blood pressure cuff on the bicep; and (3) galvanic skin conductance (literally, how much the subject sweats), by electrodes on the fingertips (White, 2001). These measurements are very important because they help to identify responses of an individual to questions he/she is asked and, therefore, it is possible to identify whether the person tells truth or lies.

There are two main types of test questions used with polygraph tests – the Control Questions Test (CQT) and the Guilty Knowledge Test (GKT). The standard polygraph is often the CQT since it is most often used in criminal investigations. The CQT often asks the suspect two types of questions – 1) Control Questions; and 2) Relevant Questions. The control questions are related to the suspect’s crime investigation, but not specifically to the crime; also they are intended to induce arousal and embarrass the suspect, making it difficult for him or her to tell the truth. Relevant questions ask specific questions about the suspect’s crime (e.g. Did you shoot the victim on April 13?). The CQT then compares responses to both sets of these questions (Lewis & Cuppari, 2009). Basically, these tests are used today because they are considered to be reliable. At any rate, these tests are used in polygraph tests as the most advanced and reliable among existing tests.

On the other hand, as it has been already mentioned above, the principle of using polygraph has not changed much since the 1920s, when the polygraph was invented. However, this does not mean that methods used in polygraph testing are out-of-date. In contrast, they are quite reliable because they were applied for a long time and proved their efficiency.


In actuality, the polygraph has a lot of proponents (Lewis & Couppari, 2009), who argue that it can be used in different fields and brings positive effects. At the same time, the high reliability of polygraphs is very important for their use in different fields. In fact, polygraphs have a number of benefits and, naturally, they can help to identify whether a person undergoing polygraph test is telling truth or lies.

In fact, a polygraph operated by a trained individual can be a valuable probative tool for an employer in testing the truthfulness of job applicants, detecting thieves, and investigating workplace crime (White, 2001). In this regard, it is worth mentioning the fact that job applicants normally fail to deceive the polygraph operator. At the same time, the polygraph allows identifying individuals, who are deceiving an employer or who are inclined to hide the truth. Therefore, employers can identify individuals, whose truthfulness is low.

Furthermore, polygraphs are particularly effective in persuading individuals to confess well hidden secrets, and when subjects are told that the polygraph suggests they are deceptive, the confession rate is consistently high (White, 2001). In this regard, polygraphs may have a considerable psychological impact on individuals. Individuals believe that polygraphs are machines, which they cannot deceive, they grow nervous and as they pass the polygraph test, the polygraph operator can identify easily whether they are telling the truth or lie. In some cases, people can tell the truth even without using polygraphs just to avoid the test because they feel so desperate that they prefer to confess beforehand and tell the truth. Therefore, polygraphs can be used as psychological tools, although such application of polygraphs is quite rare and questionable from ethical as well as legal standpoints.

Also the polygraph can unmask risks to national security. According to both the Central Intelligence Agency and the National Security Agency, the examination repeatedly produces information relevant to an individual’s trustworthiness that fails to surface in background investigations or by other selection methods (White, 2001). In actuality, the application of polygraphs to unmask risks to national security is very important because they can prevent terror attacks, for instance. Polygraphs can be used in the course of interrogations to obtain information concerning terrorists and plans of terror attacks. In such a way, polygraphs can enhance the national security because they allow finding out whether a person tells true or lies fast.

Furthermore, the polygraph is effective and reliable in what are known as “guilty knowledge” situations. Under such a scenario, an examiner administers the polygraph to a crime suspect who is tested on knowledge known only by a guilty person (White, 2001). In such a way, polygraphs can be used in quite a sophisticated way and test information and responses of an individual in retrospection on the knowledge that only a guilty person could have. In such a way, the polygraph operator can identify whether a person is guilty or not through responses of the individual to questions concerning the information known to the guilty person only.

Misuse of the polygraph

In spite of numerous benefits of using the polygraph, many specialists (Lewis & Couppari, 2009) are very skeptical about using the polygraph. In this regard, it is worth mentioning the fact that the polygraph does have a number of drawbacks because it can be misused. However, the accuracy of polygraphs depend not only on polygraphs but also on individuals, who pass the test and individuals who interpret responses. The basic disagreement regarding validity focuses on the theories that explain how a polygraph examiner evaluates physiological responses and concludes that a subject is not telling the truth (White, 2001). In fact, the problem is that the examiner’s evaluation can be erroneous or inaccurate that may have misleading results of the polygraph test. In addition, often it is difficult for examiner to make right interpretations with the help of the polygraph because of misinterpretations of the responses given by the respondent.
Furthermore, lie detectors are far from failsafe and question whether a different physiological response indicates lying or instead results from nervousness, anxiety, fear, confusion, or another emotion that may produce a change in physiological response. A subject might not be lying but can be reacting to stress, thinking of other problems, or just faking (White, 2001). In such a way, the accuracy of polygraph tests depends on multiple factors. This means that a psychological condition of an individual may affect consistently outcomes of the polygraph test. If an individual is extremely anxious, his/her responses may be misinterpreted as if the person tells lie. As a result, the polygraphs may be inaccurate, when individuals are tested in a stressful environment or inadequate psychological condition.

In addition, it is necessary to take into consideration the fact that while liars have trouble with polygraphs, so do innocent people who tend to feel more guilt, and those with greater doubts about their abilities. People with strong religious backgrounds also have difficulties with the lie detector (White, 2001). Consequently, innocent individuals may also be in trouble because they may be nervous or just because they may feel psychological pressure, when they pass the test. In fact, individuals with religious backgrounds may have the high level of anxiety and distrust as they pass the test to the machine. Therefore, their responses may be inaccurate, while results of the test may be just misinterpreted.

In fact, while polygraph examinations detect deceptiveness and non-deceptiveness better than chance, there is also a high error rate (White, 2001). The high error rate raises the question whether results of the polygraph test are trustworthy at all. In this regard, it is important to stress that errors occur because of misinterpretations by the operator or because of the condition of the interviewed person. The technical error rate, i.e. the error made because of the polygraph is relatively low. Nevertheless, the overall high error rate undermines the confidence of the public in the reliability of polygraphs, while the criminal justice system, namely courts, grows more and more concerned with the use of polygraphs because they may be useless if they admit the high error rate. Specialists (White, 2001) point out that there are two types of errors: false positives are errors that indicate a subject is lying when he is actually being truthful; false negatives are errors that indicate a subject is being truthful when he is actually being deceptive (White, 2001).

The problem is that no uniform set of operational standards exists nor are there consistent qualification requirements for examiners, even though a number of state government and private organizations monitor polygraph procedures (White, 2001). The lack of operational standards makes the interpretation of the results of the polygraph test inaccurate and erroneous. The introduction of common standards could decrease the risk of misinterpretation. In fact, if operators of polygraphs do not have common standards, their interpretations become subjective because they use those standards, which they believe to be the most reliable and accurate ones, while, in actuality, they may be far from perfect.

One of the studies concluded that other factors, including race, gender, and intelligence, could affect polygraph accuracy (White, 2001). The physiological responses of individuals with different racial background differ. In such a way, many factors may affect the polygraph accuracy that puts under a question its reliability.


In addition, specialists (Lewis & Couppari, 2009) distinguish different countermeasures individuals may use to deceive the polygraph. Successful countermeasures consist of artificially boosting responses to control questions, typically by muscular contraction or inflicting pain upon oneself (White, 2001). For instance, an examinee can bite his tongue or step on a nail concealed in his shoe to fake a reaction to the control questions (White, 2001).

One recent empirical study examined the effects of countermeasures on the polygraph test in an experiment with 120 random subjects. Twenty subjects were innocent, and of the 100 guilty subjects, 80 used either a physical countermeasure such as biting the tongue or pressing the toes to the floor, or a mental countermeasure such as counting backward by seven. Mental and physical countermeasures were equally effective and each enabled approximately half of the subjects to defeat the polygraph (White, 2001). In such a way, this study proves that the polygraph can be deceived and the results of the polygraph test are not always accurate.


In actuality, the use of polygraphs raises a number of ethical issues. In this regard, the violation of the privacy right is one of the issues that affect ethical sphere because individuals may consider the polygraph test offensive, especially in the course of the employment. Often a polygraph examination represents an invasion of privacy, especially when the coercive power of the government is behind it (White, 2001).

In addition, taking a polygraph test is a nerve-racking experience (White, 2001). At this point, it is important to take into consideration the fact that stress and stressful environment increase the risk of misinterpretation of the result of the polygraph test. In such a situation, the question arises concerning involvement of innocent individuals in polygraph tests. In fact, it is unethical to involve individuals in a nerve-racking experience, if there are no evidence of their guilt, for instance.


Thus, taking into account all above mentioned, it is important to place emphasis on the fact that polygraphs are imperfect and the risk of error always persists while using the polygraph test. At the same time, the persisting risk of error does not necessarily mean that results of the polygraph test are always wrong. In stark contrast, polygraphs can be very effective, especially, when accurate information is needed. For instance, polygraphs can be used to enhance the national security because they can help to interrogate suspects in terrorist activities. Polygraphs will help to find out whether suspects tell truth or lie. In addition, polygraphs have a number of benefits because they can help to uncover the truth, find out important information fast, and identify a guilty person. In such a situation, it is obvious that the use of polygraphs in trials is unacceptable but they can be used in the course of investigation in important cases. Moreover, the technology needs improvement to make polygraphs more reliable, while the elaboration of operational standards can decrease the risk of errors substantially.


LEWIS, J.A. & M. CUPPARI. “The Polygraph: the Truth Lies within.” JOURNAL OF PSYCHIATRY AND LAW, Vol. 37, Iss. 1, pp. 85-88, (2009).
LINDSAY, F. “5 Cops Arrested on Bribery Charges.” NY NEWSDAY, (March 4, 2005).
NELSON, J. POLICE CORRUPTION IS RAMPANT. New York: Random House, (2006).
WHITE, R.D. JR. “Ask Me No Questions, Tell Me No Lies: Examining the Uses and Misuses of the Polygraph.” PUBLIC PERSONNEL MANAGEMENT, Vol. 30, Iss. 4, pp. 483-498, (2001).