Lie Detector Tests and Criminal CasesIf you have been charged with a crime or are being investigated as a suspect, the police could ask you to take a lie detector test. You may even want to offer to take one if you know that you are innocent of committing the crime. However, you cannot be forced to take a lie detector test in North Carolina. Here, we explain why it is not a good idea to agree to take this test—even when you know that you are innocent.

What Is a Lie Detector Test?

A lie detector is also referred to as a polygraph and is a machine that measures physical attributes, such as heart rate, perspiration, and blood pressure, while a person answers questions. The operator may start the questioning process before the person is connected to the machine, and there is often a series of general questions asked first to obtain some baseline test results. Once the session is over, the test results are then analyzed by the operator for the purpose of determining the person’s innocence or guilt.

Are Lie Detector Test Results Admissible in Court in North Carolina?

Lie detector test results are in many ways unreliable. Because of this, many state criminal courts do not permit polygraph test results to be admitted as evidence. These test results are also inadmissible in North Carolina. The North Carolina Supreme Court ruled that these test results are too unreliable to be admissible in the case of State v. Grier 300 S.E.2d 351 (1983). The Fourth Circuit Court, which is the federal court that includes North Carolina, has ruled similarly.

Should You Agree to Take a Lie Detector Test?

Despite the fact that lie detector tests are not admissible in court, police officers continue to try to convince people who are suspects or who have been charged with a crime to submit to a lie detector test. If you are charged with a crime, an officer may exert considerable pressure on you to take one and could even suggest that you must be guilty if you will not agree to submit to a test. However, it is never a good idea to agree to take a polygraph test. Here are a few of the reasons why:

  • The operator could be inexperienced, which could affect your test results.
  • The lie detector machine may not be calibrated properly.
  • You may be nervous, and this could lead to polygraph machine incorrectly recording changes in your blood pressure and heart rate that suggest that you are lying or otherwise being deceptive.
  • The police want you to take the polygraph test not only to review your test results, but also to gather evidence from you. They do this through your answers to the questions during the test. In addition, they often ask you questions before you are connected to the machine and after your session is completed. Some people feel more comfortable after the test and can offer evidence or other useful information to the police—and harmful to themselves.
  • Some of the statements that you make, such as those before and after the administration of the lie detector test, can be used against you in court.

Will the Charges Be Dismissed If I Pass a Lie Detector Test?

Unfortunately, the charges against you will often not be dismissed—even if you pass the lie detector test. The police may just claim that you are a good liar. In addition, the test results would still not be admissible in court.

Are You Looking for a Criminal Defense Lawyer in Charlotte, NC?

If you are facing criminal charges, you need to speak with an experienced criminal defense attorney as soon as possible. Please contact us online or call our Charlotte office directly at 980.207.3355 to schedule your free consultation.


Howard W. Long, II
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Charlotte Criminal Defense and DWI Lawyer