Are Lie Detector-Polygraph Tests Admissible?
By Jedidiah McKeehan
You have probably seen a movie or TV show where a person is sitting in a chair, strapped up to a bunch of wires and forced to answer a bunch of questions. After each answer given, the camera will pan to a needle hovering over a piece of paper, and how the needle moves indicates whether the person is lying or not. It’s suspenseful and makes for good TV. This test goes by a few different names: Lie Detector Test, Polygraph Test, Voice Stress Analysis Test.
In my experience, it does not work quite like that in the legal world. First off, these tests are administered in private with only the tester and the subject present in the room and the tester typically tries to weed down the questions to just one or two core questions that need answers after the baseline is set up for the system to determine truthfulness. There are no questions upon questions upon questions asked during these examinations.
The first thing to know is, that the results from these tests are completely inadmissible in court. Tennessee Code Annotated section 40-17-101(b) states, “Voice stress analysis and testimony regarding voice stress analysis shall not be admissible as evidence in any criminal proceeding.”
Wait, so if they are not admissible in court, then why are these tests even administered? Excellent question. My experience with these tests is that law enforcement entities ask possible suspects to take these tests, which are inadmissible in court, voluntarily. If the suspect agrees to take the test and fails it, this allows the investigating agency to ascertain whether they are on the right track with their investigation.
In every single case where I have seen a suspect asked to take one of these tests, what they are alleged to have done is a crime related to a sexual offense involving a minor child. Even if a suspect were to agree to go in and take this test, it does not guarantee that they will not be charged with the crime anyway.
Additionally, I have had clients contact me saying they have been asked to take a test, so we hire our own tester (typically a retired FBI agent) to administer our own test, and then submit the results to the investigating agency. The investigating agency will dismiss our test results and say, “Oh, those are inadmissible anyway.” Well, why did you ask our person to take a test?
So, what is the purpose of these tests? I think they can be used as a tool to help law enforcement determine whether to pursue charges against someone, but they cannot serve as the sole basis for charging someone with a crime because the results are inadmissible in court.
Jedidiah McKeehan is an attorney practicing in Knox Sand surrounding counties.