Police and Polygraphs: Don’t Get Fooled or Tricked Into A Lie Detector Test

The results of polygraph (lie detector) tests are not admissible evidence in North Carolina courtrooms. Nor are they admissible in federal courtrooms in the Fourth Circuit, which includes North Carolina. So if you’ve been arrested on misdemeanor or felony charges in North Carolina, you have nothing to worry about from polygraph exams, right?

Wrong. It’s quite common for police or sheriffs to ask suspects to take a polygraph exam. “Look,” they may say, “if you just tell the truth, the lie detector will know it, and if you say you’re innocent, we will just let you go. If you’re really innocent, you shouldn’t have anything to fear.”

A lot of suspects will go ahead and agree to the test. That’s where the trouble really begins.

The purpose of a polygraph exam isn’t what you think

The police can’t require you to undergo a polygraph exam. They can only hope you will cooperate when asked to take one. Why would someone agree to a lie detector test conducted by the police? It could be any of these reasons:

  • The suspect is innocent, and he thinks taking the test will clear his name.
  • The suspect thinks he will look guilty if he refuses to take the test.
  • The suspect thinks he can “beat” the test if necessary.
  • The suspect knows that the results of the test can’t be admitted into evidence at a trial, so he thinks there’s nothing at risk.

Here’s the big secret: most of the time, the police don’t care about the results of the test at all. They just want you to keep talking. Sure, they have read you your Miranda rights and told you that you don’t have to answer their questions. If they can get you to agree to a polygraph exam, however, you are voluntarily waiving your legal rights.

Even though courts will not accept the results of the polygraph exam as evidence, they may admit your answers to the questions asked during the test. Read that again, because it’s a subtle distinction. The courts won’t allow the person who conducts the exam to testify that your answer to a particular question was true or false; but the question itself and your answer may both be admissible.

In addition, if you fail the test, the judge and the prosecutor will know it. The result, though not admissible can affect prosecutorial and judicial decisions throughout your case. The decisions can have a severe and negative impact on your lawyers ability to negotiate and/or try your case.

Never forget: Police do not have to tell the truth during an investigation

Even if you “pass” the test, there is no good reason to believe that you will be released and charges will be dropped. Police can—and do—say misleading things to suspects every day. After the test, they may tell you that you failed the test. They might say something like, “You said you weren’t anywhere near Windemere Road on the 14th, but the polygraph says you were lying about that. How do explain that?” It doesn’t really matter to the police that the lie detector test said no such thing. The goal is to get you to come up with a confession or a damaging explanation.

It’s not that police are evil or lazy and want to pin the crime on the first suspect that comes to hand. Rather, they are trained, experienced and talented interrogators. Often, they are convinced that they have already arrested the right person, and if they can get a voluntary confirmation that this suspect is guilty, that makes it easier to get the suspect in jail or prison. So police believe that these tactics are justified.

Getting real justice

How should you respond when asked by a North Carolina Detective, Police Officer or other law enforcement officer? "I would like to speak to my lawyer. His name is Clarke Speaks. His telephone number is (910) 341-7570. Please direct all questions to him. Thank you." 

If you are suspected of a crime, if you have been detained, or if the police or prosecutor is asking you to take a lie-detector test, say no. Tell anyone who is nearby that you refuse to answer questions without your lawyer present, and ask that your lawyer be summoned immediately. Keep saying this as often as necessary.

At Speaks Law Firm, our Wilmington criminal defense lawyers advise our clients to never volunteer for a polygraph examination without a thorough consultation with an experienced criminal defense attorney. If you are in need of a defense attorney in North Carolina, contact us at 910-341-7570 or toll-free at 877-593-4233. We have a full arsenal of legal strategies to protect your rights and to secure the best outcome for your case.


R. Clarke Speaks
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Trial Lawyer and Founder of Speaks Law Firm, P.C.
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