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Are polygraphs admissible in court?

On Behalf of | Dec 22, 2021 | Criminal Defense |

Polygraph tests, also known as lie detector tests, have a rather infamous reputation even outside of the realm of criminal law. However, many people debate on its validity as a scientific tool, pulling into question the accuracy of the results.

Though polygraph tests supposedly help determine the parties telling the truth from those who lie, in reality, it is not so easy to determine.

How do polygraphs work?

Mental Floss discusses the point of polygraph tests, how they work and why most cases will not allow them as admissible evidence. First, how do polygraph tests work? They measure the breathing, perspiration and heart rate of people as an officer asks questions usually related to a case currently under investigation. The device has sensors that attach to the arms, fingers and chest of the person in question. Spikes in any of the monitored physiological responses indicate nervousness, which in turn supposedly indicates honesty.

Why are they not used as evidence?

But criminal defense attorneys dispute this evidence, and courts no longer consider it admissible as a sign of guilt or innocence. First, polygraph tests do not actually measure a person’s honesty. They simply measure how much anxiety or nervousness they feel at the moment an officer poses a question.

Additionally, while the American Polygraph Association proclaims 90 percent accuracy, psychologists across the country estimate the accuracy rate at around 50 percent. Even police officers dispute the validity of these tests. Many opponents of polygraphs also state that the test could end up used to “bully” people into fully admitting to crimes they may or may not have actually committed. On a whole, opponents believe these tests do more harm than good.