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Should You Take a Polygraph Test? Consider These Facts First

If you get hauled into the police station and accused of a serious crime, sooner or later someone may offer you the chance to take a polygraph, which is commonly known as a "lie detector" test. Should you do it? If you're innocent, it would seem like the quickest way to get out of there and put yourself past suspicion—except these tests are virtually useless. This is what you should know about polygraphs before you agree to take one.

Polygraphs measure bodily functions, not lies.

Polygraphs don't measure the truth; they measure purely physiological reactions:

  • the amount of sweat you're producing through the use of electrodes on your fingers
  • your blood pressure and your heart rate through a cuff on your arm
  • your rate of breathing through straps on your chest

The polygraph examiner has to measure the results of each blip of the needle against so-called "control" questions, which are designed to give the reader a baseline by which to judge what's normal for you when it comes to those physiological reactions. Part of the problem is that the whole thing is very subjective—an examiner may not be that skilled at reading the polygraph's results. Plus, assumptions are made from the very start: that someone telling the truth isn't going to be anxious or nervous or react with any sort of spike in those areas to questions that offend, startle, or horrify them.

Polygraphs aren't scientific and can be easily beaten.

The American Polygraph Association probably can't be blamed for asserting its belief that the machines are 90% effective—when properly administered. That may even be true when judged by the results gained by expert examiners in controlled conditions. However, others claim the machines are really only about 65% accurate. The false positive rate is about 15% and the Supreme Court has said they aren't reliable in court since 1998.

Worse, polygraphs can be easily beaten. You can find instructions on how to beat the test online given by none other than Russell Tice, the former NSA agent who exposed the unwarranted wiretapping being done by the government. One of the country's most notorious serial killers, Gary Ridgeway, passed a polygraph. So did Aldrich Ames, the CIA agent who spied for Russia. Simply put, you can train yourself to be calm and lie your way through them (or simply be born a sociopath who doesn't get stressed easily when lying).

Police use them as an intimidation tactic and a tool.

The police know all the faults with polygraphs and know they can't put the evidence into court if you fail one, so why bother pressuring you if they aren't interested in finding out if you're innocent? Because the odds are high that you'll fail the test from sheer nervousness. Most people aren't exactly at their calmest after being accused of a serious crime, so you may fail from the stress of being asked deeply personal or outright offensive questions alone.

If you do fail, the police can ramp up the pressure and push their interrogation further by waving the results in your face. Given the cultural myth in the U.S. of the reliability of the polygraph machine, supported by TV shows like Maury Povich, who routinely uses them to "expose" liars to their loved ones, people can be easily terrified by a failed test.

Worse, the police can also lie to you—even if you pass the test, they can wave a sheaf of papers in your face full of unreadable graphs and tell you that you failed. Lying to suspects is legal, and it's done all the time. According to the Innocence Project, which tries to overturn wrongful convictions, polygraphs are an important tool in extracting false confessions—sending innocent people to jail.

Only you can decide if you're willing to risk taking a polygraph. No doubt, if you're being asked, the pressure to agree is intense. However, you should discuss the issue with a criminal defense attorney like Alexander & Associates, P.C. before you agree. He or she can advise you as to whether or not it really is in your best interest to proceed and protect you from coercive tactics and lies if you do pass.