Should you take a lie detector test?

On Behalf of | Sep 12, 2023 | Criminal Defense

If you are being questioned about a crime, law enforcement agents may ask you to take a lie detector test. It may seem like the right thing to do,  but, before making your decision, you should know some important facts.

Some experts consider polygraphs “junk science”

We often hear about a suspect failing a lie detector test or that it was inconclusive and thus provides an inference of guilt. Some experts disagree, however, and even label  polygraph tests as “junk science.”

A polygraph, or lie detector, test monitors the body’s physiological responses such as heart rate, blood pressure, breathing and sweat. The underlying theory is that when a person is being deceptive, these responses change due to stress.

But several other factors will be reflected in those physical changes:

  • Environment
  • Mental health issues, such as anxiety or obsessive-compulsive disorder
  • The experience level of the examiner
  • Bias
  • Certain medical conditions and medications

Even an innocent person may be nervous while answering truthfully. And a pathological liar may show no physical response when lying. Both of these circumstances could readily lead to inaccurate readings.

Because courts recognize that the validity of lie detector tests is questionable, their results are rarely if ever admissible in court.  Many innocent persons have been convicted because of their polygraph results, only to be exonerated later by more scientific methods, such as DNA testing.

If you  are asked by a law enforcement officer to take a lie detector test, your best option is to exercise your legal rights and decline the invitation.



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