Lie Detector and Polygraph Tests:  Are They Reliable?

By: James Davis

The bottom line is that lie detector and polygraph tests are not admissible in court, unless both the prosecution and defense agree.

This practice and limited scientific research indicates that, while sometimes the tests work, many times they do not.

Lie detector and polygraph tests are rarely used in criminal trials because they are not reliable.  If you don’t want to submit to or have the results of a lie detector test used against you, you have the right to refuse.

Being Asked to Take a Lie Detector Test?  Get Legal Help ImmediatelyAre Polygraph test reliable photo

We’ll go ahead and explain about the reliability (or lack thereof) of lie detector tests and polygraph tests, but if you have any specific questions about your individual situation or if the police ask you to take a test, contact our criminal defense law office at (904) 358-0420 or contact us online.

The Theory Behind the Lie Detector and Polygraph Tests

The theory behind lie detector tests and polygraph tests is that your body will react differently when you tell the truth than when you lie.  These tests would only work, if at all, on someone whose body reacts to the stress of lying.

The tests measure changes in pulse rate, skin conductance, blood pressure, and breathing during questioning.  The reactions to questions are compared to determine whether you’re telling the truth, or not.

The Reality of the Lie Detector and Polygraph Tests

The reality is that these tests are rarely used in criminal trials.  Both the defendant and the prosecution would have to agree in order for the test results to be admitted and this is highly unusual.

With current technologies, there is no way to determine whether the stress measured on a test stems from feeling guilty about lying or from just having to take the test itself.  (Testers try to avoid this confusion by asking irrelevant, non-threatening questions such as the day of the week or the individual’s name.)

The American Psychological Association reports, “the idea that we can detect a person’s veracity by monitoring psychophysiological changes is more myth than reality.”

In addition, if the person taking the test doesn’t feel guilty about lying or can beat the system with some physical or mental distraction, the test fails.

The polygraph is now rarely used in employment screenings because of the high return of false positives.

Where to Get Legal Help

Some people who are arrested are asked to take a lie detector or polygraph test.  They wonder whether the tests are reliable and have a fear that they may fail the test, even while innocent. It may be in your best interest to put our criminal law office phone number in your cell phone so you can always get help if you are asked to take a lie detector test or a polygraph test.  Our number is (904) 358-0420.

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