Polygraph Conundrum

Have you ever wondered why polygraphs are used by government agencies if they are not admissible in a court of law?  Ever wonder why they are not admissible in court?

The polygraph machine, which measures systolic blood pressure, was invented by William Marston, a Harvard psychologist, in the early 20th century.  This machine was based upon the idea that a person has typical levels of heart-rate, respiration and blood pressure when answering basic questions such as “Do you live at…?”  If their levels remain the same when they are asked additional questions such as “Did you kill your wife?” then they are essentially telling the truth at least that is the ideology behind the polygraph.

According to the Smithsonianwebsite, in 1922 a judge ruled that the polygraph could not be used in a murder case because it did not hold “general acceptance” among the scientific community.  This decision know as the Frye Standard has deemed the polygraph inadmissible in court ever since.  It probably doesn’t help that some individuals have trained themselves to control their heart-rate and respiration; therefore, their blood pressure and are able to deceive the deception detector.

Critics of the polygraph, point out that one major flaw is that it is unable to read thoughts and can only measure an examinee’s psycho-physiological state during the examination.  They state that the measurements also beg the question of nervousness and how that might trigger a false response.

However, the polygraph is used by many law enforcement and government agencies.

Dr. Matsumoto, psychologist, microexpression expert and director of Humintell states, “Polygraphs measure emotional arousal, which manifest in psycho-physiological reactions.  They are useful in the sense that a skilled examiner can use the box as a means to extract pertinent information.  It works because people believe it works.  Without a skilled examiner it can be inaccurate”.

In addition, recently Russian lawmakers have introduced a bill that would make the use of polygraphs admissible evidence in Russian courts of law.  In an article entitled, “Obligatory Lie Detector Tests in Russia?” it states that the polygraph could also be used to determine employment or in the termination of an employee.

The head of the Center for Political Studies, Boris Shmeley, stated, “…lie detector tests will certainly be of use, warning state officials against capitalizing on their jobs to the detriment of national interests.”  He went on to say, “For many cheating the polygraph is a piece of cake now.”  He urges the creation of a clear-cut mechanism to let polygraph examiners effectively work and respond to a variety of modern-day challenges.

So what is the perfect lie detector?  Well, from polygraph machines to fMRI’s to human lie detection “wizards” there is no one simple answer to that question.  A conglomeration of tools to detect deception for any one individual or situation is necessary to uncovering untruths.  A single, accurate, scientifically sound lie detection device would be immensely beneficial and could cut trial length times, aid in job screening, and protect borders.  However, at this point in time it just doesn’t seem to exist.

What are your thoughts on the perfect lie detector.  Is its inception in the near future?  Do you believe that a machine could be 100% accurate sometime in the future?

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5 responses to “Polygraph Conundrum”

  1. O. N. Lane says:

    Wouldn’t sexual stimulation or arousal cause the readings to spike and give false reads on the subjects records? If so,couldn’t the subject cause their facial expressions into one of “lust” whilst thinking of a romantic tryst they recently had and therefore cause the false readings. Or would that possibly cause the subject to respond inappropriately from the emotions they are feeling due to that course of action and give themselves away verbally.

  2. Russ Conte says:

    In reply, “Do you believe that a machine could be 100% accurate sometime in the future?”

    No. I’m interpreting this to mean 100% accurate in all situations. The scientific answer to that is no. Here’s why:

    Science measures things. We can be certain of length because we can measure against a fixed standard. Same for weight, mass, etc. In terms of a lie detector, we can measure perspiration, respiration, GSR, etc. There are many more examples in science.

    But truth is not an independent unit of measure. We measure the truth *against* something else. We know the man was not at the office because of a surveillance photo that proves otherwise. We know the employee is telling the truth about interviewing the applicant because all the paperwork and computer records support the claim.

    As such, there is no consistent basis on which to measure the truth. We can presently at best measure people’s reactions to questions, and that brings a whole host of well known problems. For example, if the person believes one thing, but the truth is otherwise, then virtually all lie detection methods will fail to catch that liar.

    Science would need to create a method to test truth against well defined standards, and then we’ll be getting somewhere in terms of a truth machine. Until then, such a truth machine is the realm of science fiction.

    Russ Conte

  3. Russ,
    You have some very insightful remarks. I think you make a great point when you state that measuring truth is very tricky because we measure it against something else. Also, the question of belief is another important point. If someone truly believes something does it make it true at least in the sense that our mind, therefore, body will respond accordingly with a “truth” response (i.e. heart rate remains steady no perspiration etc.).

  4. Keith D. says:

    Real truth can never be known for certain because it’s always subject to perception and interpretation. Truth and reality aren’t always the same thing, as comforting as it would be to believe they are. Because of that, like Russ said, you can’t make a machine that can measure truth 100% accurately all the time. I think anytime you encounter someone who makes extraordinary claims about a perfect lie detector, you should run away fast, or at least take it with a pinch of salt because at best they are fooling themselves, and at worst they are fooling you.

    The reason governments and some employers can and do use the polygraph is because it can be a useful tool precisely BECAUSE people believe it works. A skilled polygraph operator can use the machine to guide them to pertinent information and hot spots to make further inquiries, giving more opportunities for deception leakage to occur and lies to be found out. But it’s likely those skilled operators could learn to do exactly the same thing without the machine and with similar accuracy. A lot of it has to do with the psychological “set up.”

    Personally, I think a lot more can be learned from truth wizards than from polygraphs, because polygraphs can’t and won’t warn you against making stupid mistakes like truth wizards can. Truth wizards, at least the ones I’ve read about, are extremely careful about making a judgment of truth or deception, whereas the polygraph just draws lines representing breathing, pulse, and GSR etc. and rely on a person of relatively unknown skill interpreting their meaning.

    In employment settings, I think the only employers that are legally permitted to use the polygraph are those involving national security. And in those cases, I believe the thinking goes something along the lines of a false positive having relatively little consequence (they’re still free to get another job where national security isn’t on the table) while a false negative can have potentially catastrophic consequences like selling national security information to terrorists, so adding the polygraph is like adding a small layer of extra protection between a potential employee and a potential threat.

    The opposite side of that coin though is that we could potentially be costing ourselves some of the brightest minds working FOR national security because of a false positive result. So the question is, do you err on the side of caution or do you gamble on the side of maximum performance? It’s a tricky balance to achieve.

  5. Dan Seiler says:

    One interesting thought about why the courts don’t generally permit polygraph evidence is this. Why would we need the jury system if polygraph became acceptable? I think that polygraph is perceived as a threat to our legal system. I would bet that jury vertices have a higher error rate than polygraph. Get more information about polygraph at dannyseiler.com.

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