Why are polygraphs still used by law enforcement agencies, the FBI, and CIA?

It's a known fact that polygraphs aren't 100% accurate, and it's for that very reason that test results aren't admissible in court. Since that's the case, doesn't it make it kind of pointless to use them?

11 Answers

  • 1 decade ago
    Best Answer

    Your "known fact" is, in fact, not necessarily true. Even if it were, polygraphs are far from the only evidence in criminal cases that are not 100% accurate. Take eyewitness testimony, for example. This evidence is routinely used in criminal courtrooms and is frequently found to be unreliable. Over 30 years of social science research has documented its fallibility (see Elizabeth Loftus and Gary Wells research), yet the courts have no problem with it.

    At any rate, the polygraph, WHEN ADMINISTERED CORRECTLY BY A COMPETENT EXAMINER, is an invaluable investigative tool that can evoke information from witnesses and suspects. It has gotten a bad rap because it has been used deceitfully (suspects are told their test "indicates deception" when they have not, etc.). There are methods of administration that make the exam very reliable, at least to the level of most eyewitness testimony.

    Source(s): Professor of Psychology and Law
  • 1 decade ago

    As I'm becoming increasingly *aware* of the limitations of polygraphs, I'm starting to have the same question.

    When approached scientifically -- as I believe most important issues should be, when possible -- the evidence of the device's usefulness is underwhelming. There's little question that the machine accurately detects changes in heart rate, blood pressure, respiration and skin conductance due to perspiration, and that it's easy to correlate those changes with the time a given question is asked and answered. But there is little or no scientific evidence that these changes can clearly indicate deception, whether by trained humans or by a computer algorithm (which was created by one or more humans).

    Lying is only one possible cause for these physiological functions to change at the moment a question is asked. Others are fear, embarrassment, anger, revulsion, and so on. So while I don't doubt that polygraphs catch people in lies, I'm equally certain they catch and adversely brand innocent people, in a higher-tech corollary to the witch hunts of old.

    Moreover, the suggestion by critics that people who feel no guilt over crimes or lying -- or who delude themselves into believing their own lies -- will not have a physiological reaction to doing so, seems reasonable to me.

    There are resources available for people to "beat" the lie detector, and as one of my linked pages demonstrates (in a video) they obviously work. Thus we have a two-fold problem: the machine can be consciously influenced by the examinee, and the results can be misinterpreted by the examiner. Lie detection based on these variables is more of an art than a science.

    The U.S. Supreme Court apparently found substantial problems, as well, when it ruled in 1998 that "there is simply no way to know in a particular case whether a polygraph examiner's conclusion is accurate, because certain doubts and uncertainties plague even the best polygraph exams."

    To be fair, there is something to be said for the *deterrent* value of a polygraph, or at least the threat of one. People who would otherwise plan to enter any kind of hearing or interview intent on lying might reconsider. And one could argue for using any bit of evidence you can get, no matter how unreliable it may be independently. (Police and other law enforcement agencies also still use "psychics," though there's no evidence *they've* ever helped anyone find the truth, either!) But unless the polygraph test is taken as one bit of a whole picture and not by itself, there's a real danger of both *missing* lies and "seeing" lies that aren't there.

    Source(s): Polygraph Testing and the DOE National Laboratories http://www.sciencemag.org/cgi/content/full/290/549... National Academy of Sciences report says polygraph testing too flawed for security screening - Skeptical Inquirer http://findarticles.com/p/articles/mi_m2843/is_1_2... http://www.skepdic.com/polygrap.html (with a video: Michael Shermer Tests the Polygraph) Scientists: A good lie detector is hard to find - M.I.T. http://web.mit.edu/newsoffice/2007/lying.html The Truth About the Polygraph - Salon http://archive.salon.com/health/feature/2000/03/02... Ask Bill Nye - Encarta http://encarta.msn.com/encnet/features/columns/?ar...
  • Anonymous
    1 decade ago

    While not admissible, they are very useful for interrogation purposes. And they are not as unreliable as people think. A few articles have shown that a polygraph is more accurate than an in-person line-up - and line-ups are admissible!

    Also, polygraphs are frequently used to dismiss charges against people. For example, if you were charged with a crime that you know you didn't commit, you might ask for a polygraph test. Most prosecutors would dismiss the case if you passed.

  • 1 decade ago

    Polygraph results are admissable in court if both sides agree to it. They aren't 100% accurate but what in life is? They are a very valuable tool and they can be used to eliminate a suspect as well as develop a suspect. They are a tool for information and indicators that an investigation is going in the right direction and then additional evidence can be obtained. Polygraphs are very accurate when used correctly.

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  • 1 decade ago

    Polygraph results are used as a tool for interrogation, even though not admissible in court. It can give investigators an idea of how truthful, or not, a subject may be. Therefore, it is not pointless to use polygraph tests.

    Source(s): Police Academy class.
  • 1 decade ago

    Every body gets the jitters when they know they have to take a lie detector test. When you have the jitters you are not at your best and police have a way of putting you off your game when they question you so you will make mistakes and they can trap you into revealing things you perhaps feel are better left unsaid.

    it give them new leads and they need all the help they can get legally because as the law they must abide by the law whereas the criminal does not.

  • 1 decade ago

    yeah I dont think its a perfect system at all because they arent completely accurate. But they do get the majority of people who are lying. So I guess agencies that use them would rather lose some cantidates that were telling the truth then unknowingly hire hundreds of liars.

  • 1 decade ago

    while they are not admissible if challenged under expert witness, they do tend to be some what accurate as such are part of the process they use, just one step in the investigation

  • Anonymous
    1 decade ago

    well those things that they stick to you yea measure your blood rate and heart rate when people are asked questins and they answer wrong there heart speeds up

  • Kevy
    Lv 7
    1 decade ago

    To see if you are honest or not.

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