Broken,

You ask if several suspects are polygraphed regarding a crime and all are found to be deceptive on a polygraph exam, what are we to think?  In theory, (1) all may be guilty (all true positive polygraph results, (2) all may be innocent (all false positive results), or (3) one or some subset of the total may be guilty (leaving those to be true positive results and the balance to be false positive results).  I believe what you would really like commentary on though is if the current prime suspect is guilty and all others are innocent, what are we to think of a situation in which all are polygraphed and all are to be found deceptive.  

I believe with a control question test polygraph exam this is par for the course.  In general, the public and polygraph examiners themselves are largely blind to their own errors (they tend not to believe or to dismiss denials from innocent suspects who have been found deceptive on a polygraph exam and in general do not receive much feedback regarding their errors).  There are two types of exception to this largely unrevealed and blind error. They are when (1) a person is found to be deceptive, that person denies his involvement, and a different individual subsequently confesses (with corroboration) to the investigated crime, and (2) a situation in which numerous people are polygraphed who might have had sufficient access to commit the crime, many or all are found to be deceptive, but they are unlikely to have all committed the crime.  

This latter sort of revelation has frequently happened with a scenario in which all of a bank's tellers being polygraphed in regard to a bank burglary or all of an armored car company's employees being polygraphed regarding an armored car robbery are each found to be deceptive.  Although I did not participate in the investigation nor conduct any of the polygraph exams given, I was made aware of a similar situation in which a large number of individuals were polygraphed regarding the murder of an FBI agent.  Again a control question test produced what later turned out to be numerous false positive results; as I recall, the matter was ultimately resolved using a concealed information test.  The reason to suspect the initial CQT exam results to begin with was that there was no plausible reason to expect everybody to be guilty or complicit in the crime.  Why do these sorts of false positive results occur, only to be realized within these narrow circumstances?  Again, I believe it is due to fear of consequences (of being found deceptive—not a fear of being caught in a lie) and the obvious connection between those consequences to answers to the equally obvious relevant issues/questions (burglary, robbery, and murder, respectively).  I suspect if the scenario I believe you to be asking about is the one which actually occurred, this later (of two explanations) may well be the source of the revelation and fear of consequences may be the mechanism for any false positive results that may have transpired with the polygraph exams.  Again, because all of the facts are not publicly known (or at least known to me) it is hard to do anything but speculate at this point regarding the specific case you refer to.

Regards,

Drew Richardson

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Any chance his actual charts would be made available to him?  It would be nice for the taxpaying public to verify that "Quality Control" is doing its job correctly.

Skeptic