Never Consent To A Lie Detector Test

Posted in Deception by David on July 31, 2009 1 Comment

Why You Should Never Consent To A Lie Detector Test:

David A. Camp, Ph.D.

For most of us the lie detector exists as techno-sorcery, shrouded in myth, misunderstanding, and ultimately holds many false beliefs and fear.

What are the facts? How do these machines work? Why should you never consent to such a test?  Let’s open the hood on the lie detector, learn how they work, what they can do and what they can’t. Then you will see what can happen if you take one.

First of all, there is no such thing as a lie detector machine. What most people think of when they refer to a lie detector is a technological stress identification device known as ‘the polygraph’.  The polygraph is a machine that collects and measures stress changes as a person answers questions asked by a polygraph test administrator.  In short the polygraph does three things. It measures stress, increases in stress, and decreases in stress. That’s it! The lie detecting ability of these machines is completely based on the ‘belief’ that when we lie we feel stress.

The polygraph is a set of instruments that measure and record physical functions related to stress. These include pulse rates (how fast your heart is beating), blood pressure levels (how powerfully your heart is beating), breathing rates (how fast you are breathing), lung volume (how deeply you are breathing), and galvanic skin resistance (how much sweat your skin is producing).  All of these measures increase when we feel stress. So we measure stress, so what? If these measures show an unusual increase in detected stress during questioning, the answer given when the stress was measured is assumed to be a lie.

Why does deception cause us stress?  There are three reasons:

  1. During our childhood most of us are taught that lying is wrong. We feel stress because we are ‘breaking the rules we were raised with’.
  2. When we lie, we have fears of being labeled a liar because we most often base our self-perceptions on what we believe others think of us.
  3. When we lie, there is often a fear that we may be punished.

Many myths about lie detectors exist and some are actually (but incorrectly) included in college textbooks on human behavior. Three of the more common myths are:

  1. Drugs and alcohol can be used to beat the machine
  2. Refusal to take a polygraph means you are guilty
  3. The machine is infallible

Drugs And Alcohol Can Be Used To Beat The Machine

Although drugs and alcohol do affect our mental and emotional states, they do not work as an effective countermeasure (a way to beat the machine). However, the test is often less effective if you are asked about something you did while you are intoxicated.

Generally, beta blocking anti-anxiety drugs may decrease the machine’s ability to measure stress. However, there is a lot of variability in how these medications affect the test.

Warning: any attempt to beat the machine, if discovered, will be considered a sign of guilt. So trying to beat the machine is not recommended if you are going to be tested.

Refusal To Take A Polygraph Means You Are Guilty

What are the likely results of taking a polygraph test? If you take it and it works like it is supposed to, your claims of truthfulness are supported. Legally though, it doesn’t matter how it turns out since the results can’t be used in court.

If you refuse to take the test in a criminal investigation, there are no legal repercussions. However, if you are concerned that those around you may think you are hiding something, you can show them the facts of polygraph error rates, thereby justifying your decision. For the most part, consenting to a polygraph test only serves the media as a way to socially convict you outside the courtroom.

On the other hand, if you take a polygraph test for a job, there is no court to say that the evidence is not admissible. In other words, if you take the test and fail, it doesn’t matter if you lied or if the machine was in error. Your potential employer will assume you’re a bad risk will not hire you.

So what can you do? Discuss the problems of the test with the employer. If the test is still insisted upon (legally – see below), then you may be able to request a specific type of polygraph test (the GKT mentioned below) if it is appropriate in that situation.

The Machine Is Infallible

Lie detectors possess many problems. The two most concerning are that lie detectors rely on stress and the error rates of lie detectors are high.

Although stress does occur when we lie, there are many other causes of stress. Stress can come from fear, physical ailments, uncertainty and even concerns about taking the test itself. In other words, polygraphs are great stress detectors, but they DO NOT detect lies. Concluding that stress is due to lying is fantastic leap of faith. In fact, studies suggest that these tests could be wrong in 4 out of every 10 tests.

The second major worry is that polygraph testing seeks to identify lies, not honesty. Thus if an error is made, most of the time it will say that your truthful answer is a lie.

Polygraph Facts

The American Polygraph Association (APA) claims that their tests show a 98% accuracy rate. In properly conducted research, those with a vested interest should never conduct the testing since they may (even unconsciously) sway the results. Those involved with the APA have a vested interest.

What about properly conducted studies?  Objective and unbiased studies show the polygraph to have an error rate of almost 40%.

If these facts are insufficient to convince you, try these views:

  1. Retired Supervisory Special Agent Dr. Drew C. Richardson (who holds a doctorate in physiology, was funded by the NSA for his research on polygraph components, collected data for the DOD Polygraph Institute (DoDPI) and prior polygraph examiner for the FBI testified before the United States Senate in 1997 that, “ Polygraph screening is completely without any theoretical foundation and has absolutely no validity [and that] there is almost universal agreement that polygraph screening is completely invalid and should be stopped.”
  2. Dr. Eric Haseltine (PhD in physiological psychology) past head of research and development for the National Security Agency and associate director for science and technology for the Office of the Director of National Intelligence: “it is a big leap to claim that a person is lying [based] on a physiological response. . .  I personally would not put a lot of stock in any of these measures, including polygraphy per se.”
  3. Retired CIA polygraphist John F. Sullivan stated that the “Polygraph is more art than science, and unless an admission is obtained, the final determination is frequently what we refer to as a scientific wild-ass guess (SWAG)”
  4. Former CIA Director John M. Deutch stated that “[The CIA's] reliance on the polygraph is truly insane”. And Last but not least
  5. Former CIA Director R. James Woolsey, “…the use of this highly flawed instrument should be radically curtailed.”

However, if you still want to know more about the polygraph and its workings – read on.

What are the Polygraph Test Errors

The most common errors are ‘false positives’, ‘false negatives’, ‘operator error’, ‘mechanism malfunction’, ‘improper subject preparation’, and ‘interpretation error’.

False positives and false negatives are the errors of greatest concern. False negative errors indicate that a liar is honest while false positives indicate that a truthful subject is a liar. Since the testing is focused on finding deception rather than truth, false positives are the greatest concern.

Error rate testing found that errors occurred between 23% and 38%. In other words, if the test makes an error, it will most likely say that you are a liar when you were telling the truth. In fact this can occur as much as 37 out of every 100 tests.

Types Of Polygraph Tests

Most everyone agrees that polygraph tests are good measures of stress (even if they aren’t good lie detectors). Even if the machine was valid, how a person is tested can make a great difference in the test results. To provide the best results possible, many types of questioning procedures have been developed. Two test methods lead the pack. The Control Question Test (CQT) and the Guilty Knowledge Test (GKT).

The Control Question Test (CQT)

The Control Questions Test (CQT) compares the answers to questions like, “Have you ever stolen money?” and “did you rob this bank?”  This is the most commonly used test.

Another very serious concern is that if you fail this type of test, you will be considered a liar and assumed to be probably guilty. When evidence such as a polygraph leads police to believe that someone is guilty, they often begin an interrogation. Although interrogation today does not use torture and such, it does rely on powerful coercive psychological techniques that have been shown to have a great potential for producing false confessions (even in rational and innocent people).

The Guilty Knowledge Test (GKT)

Unlike the CQT test, the guilty knowledge test (GKT) is strongly supported by research findings. It measures stress, but does so in an innovative manner. The examiner uses groups of questions about the crime offering several possible answers. Since only one of the answers is valid and the rest are decoys, a guilty person will show stress when the right answer is mentioned because at the sound or sight of the correct answer their fears are aroused and the machine will show increased stress.

For example, when asked what weapon was used, an examiner might give choices such as “none, a knife, a screwdriver, or a gun”. Since the innocent don’t know the answer, they will show no abnormal stress on any of the offered answers. Each question has four possible answers. If an innocent person inadvertently reacts to one of the answers, there is only a 1 in 4 chance they will react to the correct answer. If two questions are presented, the chance of them accidentally reacting to the correct answer on both questions is 1 in 16. When eight questions are used, the odds are 1 in 32,768 that an error has been made.

The studies on the GKT test shows accuracy rates of 84% in identifying guilty subjects and it is correct identifying innocent persons 94% of the time. Thus, if this test can be used (in situations where questions like these can be asked), this method produces the fewest errors. Unfortunately the GKT has not been widely accepted and used by examiners.

Polygraph Testing Procedure

Regardless of the test used, the polygraph test should be given in a location that is private without distractions and with only the examiner and the subject present. The examination has three phases:

  1. In the pretest phase the examiner completes the initial requirements: paper-work, background information on person, establishing rapport with them and informing them about what questions will be asked during the actual test.
  2. In the chart collection phase, questions are asked and the machine records stress levels.
  3. In the follow-up phase, the subject has an opportunity to explain questionable responses. However, since the final conclusion is based on the examiner’s interpretation, anything the subject says to the examiner could make things worse.

Who Can Use The Polygraph And When.

Because of the errors in polygraph results, they are generally not acceptable in a court. With respect to employers, the 1988 Employee Polygraph Protection Act (EPPA) prohibits most employers from using polygraphs to screen job applicants. If they want you to take a test, they are in violation of the law (unless they are one of the exceptions). The exceptions to the EPPA include police, government workers and subcontractors, security companies, those involved in public health and safety, those that deal with controlled substances and businesses involving large risks (such as armored car drivers and banks).

Summary And Conclusions:

The polygraph is an effective, but imperfect, tool. Although it produces results somewhat better than chance (as high as 80% but as low as 58%) those results often rest on the examiners interpersonal skills. These are all good reasons to consider avoiding taking the test if it is not absolutely necessary.

For more the use of lie detection in professional applications (i.e. law enforcement, business, human relations, etc.) visit http://www.exposingdeception,com

Teenage girls (or their parents) can find social survival skills, safety tips, rules of human behavior and more at:

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