Culin Sharp Autry & Day, P.L.C.
Northern Virginia Office
4124 Leonard Drive
Fairfax, VA 22030
Phone: 703-934-2940
Fax: 703-934-2943
Piedmont Region Office
67 West Lee Street
Suite 101
Warrenton, VA 20186
Phone: 540-349-1900

Criminal Defense Frequently Asked Questions

Q:   I am a suspect in a criminal case. The police have asked me to take a lie detector test to “clear my name.” What should I do?

    What is a “Lie Detector” Test?

    A “lie detector” is also called a polygraph. A trained operator hooks a machine to you, and measures your pulse, breathing, skin temperature, and other vital signs while asking you questions to which you are supposed to give a simple “yes” or “no” answer. The operator sets up the machine by asking you a series of innocent or “control” questions, and asks you to answer some of them falsely. Your physical responses when giving the “false” answers are measured and compared to your responses to the actual questions which come later. The polygraph prints those responses on a long sheet of graph paper which is then “read” by the operator.

    In police work, after the operator concludes the session, he takes the paper to another room, out of your presence, and analyses it. He may have another trained colleague review his results. After some period of time, he returns to advise you of the result. Some operators may claim you were lying, even if the results were in your favor or inconclusive. This action is based on the theory that many test subjects, convinced of the polygraph’s reliability, may think they have been caught and then confess on the spot. In short, the polygraph is a tool to extract confessions from criminal suspects.

You should always consult with a lawyer about the advisability of taking a lie detector because the process is designed to give the police every advantage, as outlined below:

1.    Polygraph results are considered so unreliable that in Virginia, they cannot be admitted in evidence at a trial. The judge will not let a jury hear whether you “passed” or “failed” the polygraph test. In fact, the jury cannot even be told if you refused to take the test. If the test results cannot convict or clear you, why would you agree to submit to a polygraph examination?

2.    Unless you are very sophisticated, you have no real idea how the polygraph works. You have no training in operating the machine and could not tell if it has been calibrated and set up correctly, to say nothing about whether it has been properly maintained. This issue is also a strike against the credibility of using a polygraph in a criminal investigation.

3.    The polygraph operator is not only trained to operate the machine. He is also trained as an interrogator. In fact, he may ask you questions before or after the session, all with the aim of gathering evidence. Most subjects have no training in how to answer police questions. In such a situation, the operator is the professional and the subject is the amateur. The subject is therefore generally at a disadvantage during the polygraph process.

4.    The polygraph operator knows the law and the questions he needs you to answer before he starts the session. The subject generally does not, which places him or her at a significant disadvantage during the testing.

5.    The polygraph operator usually conducts the test at police headquarters, his “home turf.” Here, he has the advantage of having other people and resources at his disposal. He determines the temperature and lighting of the room, where you sit, who can be in the room with you, and other factors. You generally have none of these advantages and no one to help you if you have difficulty. Your only choice is to end the test, which most people think will convince the police of their guilt.

6.    Your responses to the operator’s questions are either “yes” or “no.” The polygraph does not interpret lengthy explanations so you have no chance to discuss why you answered a question in a certain way.

7.    Although the results of the polygraph test are not admissible as evidence in court, your responses to the questions are. Therefore, any statements you make during or after the polygraph session can be used against you. If you are not considered to be “in custody” during the test, the operator is not required to advise you of your rights to remain silent or to consult with a lawyer before answering any question.

8.    Remember, a lie detector test is a tool designed to gather evidence. Whether that evidence comes from the pre-test questions, the post-test interview, or the test results themselves, the test is designed to help the police gather enough evidence to charge and convict a suspect of a crime. If you are asked to take a lie detector test, the police likely think you are that suspect. You should consult with a lawyer any time such a request is made of you.