How Reliable Is A Polygraph Machine

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The polygraph machine, invented in 1921 by a Berkley medical student, is a machine that measures various biological functions in the body with the hope that the biofeedback will change when a subject is trying to deceive a questioner. The machine measures blood pressure, pulse, skin conductivity, and respiration. The scientific community has wavering views as to whether the tests are accurate at measuring deception. Manufactures and technicians believe that the machines are about ninety-five percent accurate; whereas many unbiased opinions believe that number is closer to the mid-sixties. Knowing whether or not these machines are credible is immensely important due to their use in everything from military interrogations to television shows. These machines need to be proven accurate or not used.
One of the main functions of a polygraph test is to provide evidence for one side of a court case. In this scenario it is vitally important that the test be definitive because people's lives and livelihoods are at stake. Sadly, these test are not without fault and at times they are completely wrong. In the court case of U.S. v. Shaffer, the polygraph test showed that there was no deception when the respondent said that he had never consumed drugs during his tenure in the armed forces, yet his urine tested positive for methamphetamine[1]. In other cases the tests can say that there is deception when none exists.
Willian Iacono, a University of Minnesota professor, was quoted saying that polygraph tests "may be useful as an investigative aid and tool to induce confession, it does not pass muster as a scientifically credible test[2]." In conclusion the use of these tests in everything from court, to interrogations, to television must be conducted by the most skilled operators and the results must be viewed as aids but not definitive answers.

1. http://www.law.berkeley.edu/faculty/sklansky/evidence/evidence/cases/Cases%20for%20TOA/Scheffer,%20United%20States%20v.htm

2. http://www.psych.umn.edu/faculty/iacono/2001%20forensic%20lie%20detection%20-%20procedures%20without%20scientific.pdf

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This page contains a single entry by cunni350 published on November 20, 2011 3:57 PM.

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