Intrigued,
Any admission you make to your polygrapher has the potential to be spun out of all proportion into a damaging -- and perhaps disqualifying -- admission. See the subchapter titled "Inflation/Fabrication of Admissions" beginning on page 58 of the 2nd edition of
TLBTLD for examples of this. You'll need to make a judgment regarding the potential for any admissions you make to be inflated or mischaracterized by your polygrapher.
Note that in a pre-employment polygraph setting, any question about drug use is almost certainly a
relevant one. Admitting your one time marijuana usage is very unlikely to disqualify you -- probably most Americans who grew up after the Second World War have experimented with marijuana, and employers typically allow for a limited amount of past marijuana use. For example, the FBI allows for marijuana use of no more than 15 times, with no use in the past three years.
If you admit to your one time marijuana use, make it perfectly clear that it was one time
only. Don't fall for the interrogator's trick described in the subchapter "...And Sign No Statements" (at p. 110 of the 2nd ed.):
Quote:A common tactic used by polygraphers is to request the subject to write out and sign a statement listing the admissions they have supposedly made. It may not be in your interest to sign any such statement. Suppose, for example, you admit during your "pre-test" interview, or in the pre-polygraph questionnaire that some law enforcement agencies require applicants to fill out, that you smoked marijuana three times while you were in high school. Your polygrapher asks, "Can you really be sure that it was only three times? Any doubt in your mind will show up on the polygraph. Would it be fair to say that you used marijuana less than ten times? Yes? Then very well, why don't you write that down here and sign."
When you sign that statement saying that you used marijuana "less than ten times" instead of the three times that you said earlier, you've just given your polygrapher a signed "confession" that he can use to portray you as having been dishonest when you claimed to have used marijuana only three times.
The countermeasures described in
TLBTLD can help to assure that your physiological responses to the "control" questions are stronger than your physiological responses to the relevant questions. But they will be of little use if you make a disqualifying admission, or if an innocuous admission you make is spun out of proportion by the polygrapher.