Gavin,

While a sedative might reduce a person's overall reactivity, one would not expect it to be of great help in passing the most commonly used polygraph technique, the "Control" (or Comparison) Question Test. In this technique, the examinee's reactions to relevant questions (for example, "Did you shoot John?") are compared to the examinee's reactions to so-called probable-lie "control" questions that everyone -- even a person answering the relevant questions truthfully -- is secretly expected to answer with less than complete honesty (for example, "Did you ever intentionally hurt someone?" or "Did you ever lie to get out of trouble?").

If the examinee's reactions to the relevant questions are stronger, the examinee fails; if reactions to the "control" (or comparison) questions are larger, the examinee passes. So the key to passing is to show stronger reactions to the control questions than to the relevant questions, and this is something that a drug like valium is unlikely to accomplish.

For a fuller explanation of polygraph procedure and countermeasures, see Chapters 3 & 4 of The Lie Behind the Lie Detector.

No no just happen to have the same names thats all, quite a popular Dutch name...

Ah thanks that great. I find the countermeasure idea extremely interesting.