Is it possible...

[depressed]

..that those in prior/current LE who take a poly for another agency and fail due to the "drugs or serious crime" portion, even though they have never committed one or used drugs, are subconsciously projecting their past work experience (which involved such issues - dealing with drugs and serious crimes from the public) into this question, and thus a "spike" in the question/answer (as deceptive)?

[George W. Maschke]

I suppose that's possible, but it's hardly the only--or even necessarily the most likely explanation for a false positive outcome in such a situation. Polygraphy has no scientific basis, and it should surprise no one when such an invalid test produces erroneous results.

[depressed]

Why then do some fail on certain questions but not others when they have not done what they are being told they are lying about?

[George W. Maschke]

Why then do some fail on certain questions but not others when they have not done what they are being told they are lying about?

That's kind of like asking why a particular coin toss came out heads rather than tails. That said, polygraph operators know, for example, that illegal drug use is much more common than, say, espionage. Polygraph units that question applicants about both topics are going to flunk many times more applicants on the former than the latter because they know that the former is much more common in the applicant population.