Comparison of Procedural Accuracies. A Comparison of Polygraph Accuracy to other Procedures and Evidence. The field of polygraph has been plagued with controversy and conflicting opinions since its conception a hundred years ago. Despite this the use of polygraph has been maintained and in some ways expanded. There have been plenty of misrepresentations of the facts as well as emotionally charged opinions about its use and the theory behind it. In this Article “Comparison of Procedural Accuracies” we compare some of the studies about accuracy of medical procedures and other evidence.

I tend to see in the arguments against its use a general rejection of the idea that a machine can make a decision on a human being’s truthfulness in their statements. It would seem there is a very concerned part of our psyche that wishes to reserve a human being’s ability for deception as if it were a right and to resist the idea that a human being’s inner feelings can be interpreted by a machine. This concern can seem understandable if you consider the fact that deception is prevalent in our society in several well entrenched ways that have some sort of well intent or at least personal interest behind them. Lies of social lubrication and social obligation, lies to protect someone’s feelings, lies to avoid an uncomfortable conversation, lies to gain employment or social status. There is no shortage of motivations to reserve the act of deception as some sort of personal liberty.

There are those who would also resist the inclusion of polygraph examinations as evidence as it would no doubt simplify a tedious and inefficient process such as legal proceedings which would not be to the legal community’s benefit.

Interestingly human beings do not seem to exhibit this resistance with the notion of “just because I have the symptoms does not mean I have the condition” when it comes to medical procedures or other types of evidence. Rarely would the average person ask the question of how accurate an MRI or fingerprint evidence actually is and they would be less likely still to dispute it. This information does not present us with the same kind of existential threat as that of a polygraph examination.

One such study compared the accuracy rates of some mid grade polygraph studies to those showing the accuracy of several different medical tests or psychological diagnosis tools. Polygraph accuracy of these studies ranked among these processes with similar accuracy and above some of the diagnosis tools used by psychologists who are often vocal critics of the polygraph. The table showing this comparison is below.

Crewson, Philip. (2001). Comparative Analysis of Polygraph with Other Screening and Diagnostic Tools. 161.

A collection of study findings shows the comparable accuracy’s of medical tests or other types of evidence. These studies show that:

7.5% of hospital visits in Canada have a medical error.

33%-100% is the range of accuracy for abdominal ultrasounds depending on the condition being tested for and a variety of other factors.

95%-99% accuracy in ultra sound fetal sex identification depending on age of fetus, position and technician experience.

20%-97% accuracy in witness testimony depending memory, confidence and influences on the witness.

73%-99% accuracy in fingerprint identification depending upon fingerprint quality, examiner experience and contextual bias.


There has also been shown to be errors made in dna evidence due to contaminated samples or more than one source of dna in the sample.

 Despite this it would still be prudent to make decisions with the help of scientific testing and evidence. Not test is perfect however when a decision has to be made the individual can benefit from the knowledge and probability of scientific testing. It would not be considered diligent to make a decision and do so without the aid of the probable accuracy that scientific testing provides us even if it makes us uncomfortable to do so.

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Sources used for this article

CMAJ. 2004 May 25; 170(11): 1678–1686.

doi: 10.1503/cmaj.1040498

BMJ 2016353 doi: (Published 03 May 2016)


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Pacheco et al., 2014