It is common for people to fail a polygraph interview for a security clearance and then later pass with no difficulty. I can assure you that if you drop me into a chair and start questioning me, I will mostly likely exhibit every guilty sign that there is unless I medicate to avoid the signs. I am also naturally fidigty (as if that were a word) so I have had security people follow me around since they were certain that I was up to no good. Of course after I figured out what they were doing, I opted to have a little fun with them and ran them all over the place. I almost felt bad for them.... "where is he going now....".