Johnn wrote on Sep 14
th, 2005 at 6:53am:
Thanks, Bill for your advice - I've sent you the PM.
Sometimes, I'm under the impression that polygraphers orchestrate sessions - such as not passing you on purpose if you failed the first polygraph. Why should they prove each other wrong? I've read polyfool's story, and this seems to be the norm. In any case, I'm still looking forward in applying your advice.
Frankly, I think there's another explanation, and it points to a problem that's not limited to the polygraph.
Police interrogators are often confident that they can discern lies from truth, even though research seems to indicate that they're actually slightly worse than the average person at doing so. Thus, they may believe they can determine a subject's innocence or guilt, based upon conclusions regarding his truthfulness.
I would imagine that this failing applies to polygraphers, as well. Whatever the source, if an interrogator believes a subject is guilty, that belief is difficult to shake, and in large part guides the rest of the investigator's actions. For polygraphers, an irrational belief in the accuracy of the polygraph would likely lead them to conclusions regarding the subject's truthfulness before the session even begins, if a prior polygraph session indicated one way or the other, even though the polygrapher might be required to "demonstrate neutrality". At the very least, subconscious assumptions about the subject's truthfulness could lead to confirmation bias in interpreting the new results.
As an aside, an assumption of guilt and some of the interrogation tactics that are brought to bear as a result is one of the prime reasons false confessions are elicited, with or without the polygraph. Once an investigator assumes guilt, he or she will proceed to interrogate, rather than interview, and will sometimes use whatever means necessary (hopefully within the law, but that still allows a lot of leeway) to get that confession. And interestingly, one common way in with false confessions are generated is the presentation of false evidence to the subject that implicates him or her, or otherwise creates a belief in the subject that denial of guilt is useless and that things will actually be better by confessing. As you might imagine, the confronting of a subject with a polygraph result of "DI" could easily meet this criteria.