Barry_C wrote on Oct 19^th, 2007 at 3:06pm:

There's no way you could know that, and experience speaks against it.  The beauty is, even if true, the research shows it doesn't matter if I can spot them or not as the guilty still fail in spite of their attempts.

What is it that leads you to believe that any significant percentage of people who attempt countermeasures are caught doing so?

It seems that the reason examiners believe CM's are detectable is because a percentage of the subjects they accuse of using CM's admit to doing so.  Am I correct about that?  Countermeasure detection data comes from those subjects who are accused of using CM's and admit that they did?

If countermeasure detection data comes from another source, such as the number of people accused of countermeasures (without any admission of same by the subject), how accurate could that be?  What's the difference between a guess regarding CM usage and a guess regarding truth or deception?

If the data comes from subjects who are accused and admit to using CM's, how accurate is that?  I'm sure the number of people who admit to CM use can be quantified, but my point is that you have no idea what percentage of people actually used CM's - you only know the people didn't use them well and who were foolish enough to admit to them when accused.

For example, 100 people are given pre-employment polygraph sceening exams, and 50 of those people produce charts that (in the examiner's opinion) indicate no deception and no use of countermeasures.  The other fifty subjects are accused of lying and/or countermeasures, and twenty of those people admit they had been using countermeasures.  

Based on what has been written here before, the examiner would take that example and tout it as proof that countermeasures are detectable and don't work anyway.  But how do you know the true number of people who were using countermeasures?  It could have been the twenty who admitted to it, the fifty who were accused of it, the fifty who showed no deception at all, or (most likely) some combination thereof.