wrote on Jun 25^th, 2011 at 1:26am:

Those tubes can tell when  you don't breath even for a split second.  And the fact that the polygraher is staring at you, don't even think about tongue biting or nothing stupid.  There is a sensor on the seat, so don't try the anal contraction.  I was busted.  I thought they were just accusing me of CMs as standard procedure but in the end I was rejected and got a statement saying that was why.  They knew.  I denied it.  But they knew.

TLBTLD does not recommend anal contraction as a countermeasure. In fact, given the non field-tested sensor on the seat it advises against it.

They did not 'know' you were using countermeasures; your polygrapher took a stab in the dark, rattled you and you folded.

On my first polygraph which I successfully passed using countermeasures the polygrapher used one of the counter-CM tests, so it was obvious he suspected something. I kept my cool, finished the test and 'passed.'
He didn't 'know' anything though I'm sure he had his suspicions.