The Truth about Lie Detector Tests


There is no such thing as a lie detector test. Let me repeat that. There is no such thing as a lie detector test. However, there is such a thing as a polygraph examination. And the use of polygraph examinations in law enforcement and security services have created a $2 billion dollar industry despite the fact that Polygraph tests have been determined by scientists and Courts to be highly inaccurate in detecting lies, or even truth. As succinctly stated by The American Psychological Association, “Most psychologists agree that there is little evidence that polygraph tests can accurately detect lies.” So why are polygraph tests so popular in law enforcement arenas? Because law enforcement officers play upon an accused person’s hope that he or she can prove his or her innocence by just telling the truth. Sadly, most people who act upon this hope, and tell the truth while taking a polygraph examination, are still charged with a crime and the polygraph results are used against them. You might ask, “How can this be since courts and psychologists agree that polygraph tests are scientifically invalid?” This is how: Before permitting the suspect to tell the truth to a polygraph examiner, law enforcement officers will often require the accused person to sign a document permitting the State to use the polygraph results against them in Court. Their reasoning is, “if you’re so sure that you’re telling the truth, you shouldn’t have any fear of putting your money where your mouth is.”

So, what is a polygraph examination? A polygraph examination relies upon a machine that is a rectangular box that has sensors attached to wires. These wired up sensors are then attached to different areas of the body to instantaneously record on paper a person’s blood pressure, pulse, respiration and skin conductivity. A “trained” polygraph examiner will ask the examinee questions, and the examiner will look at the recordings of the physiological reactions. Most often, even when a person is telling the truth about the details of what they are accused, the results will be interpreted by the examiner as “Deception Detected.” How is that possible if the examinee told the truth? The answer is simple.

Since a polygraph machine is only recording physiological states of change in the respiratory and blood flow operations of the body, how can that demonstrate that somebody is lying? It can’t. Think of a time when you were minding your own business and not aware of breaking any laws. And, even though you were unaware of breaking any law, you were pulled over or approached by a police officer. In this scenario, without having any words spoken, when did your body start making physiological changes? In my case, it was when I was pulled over by a Michigan State Police officer, it was before I knew that I was pulled over for a “dim tail light.” Now, my Mother would have characterized my physical reaction this way, “You must have done something wrong or you wouldn’t have a guilty conscience.” And, even though it’s true that every human being is guilty of something, it’s not always true that a human being accused of something is guilty of that which they are accused. Which goes to my point that “law enforcement officers play upon an accused person’s hope that he or she can demonstrate his or her innocence by just simply telling the truth.” Rules to Live By.

  1. If anyone in law enforcement suggests or asks that you take a polygraph examination “so that you can prove your innocence,” you tell them, “No.”
  2. Say nothing more than. “I want to call my lawyer.” and then,
  3. Immediately call a lawyer you trust.

Your life and your future are too important to ignore your Constitutional right to remain silent. There is no such thing as a lie detector test. However, history has demonstrated that the best way to let the truth shine through is a vigorous cross examination by a seasoned trial lawyer.

If you have questions about a matter that is pending before a court in Northeast Indiana or Northwest Ohio, contact Matt Chapel immediately. Call Matt at 260-387-6236 or email him at

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