On Talking to Polygraphers

According to an AP Story, a state polygrapher testified yesterday in the Scott Peterson murder trial that on the day after his wife disappeared, Peterson told the polygrapher (falsely, it would seem) that Peterson was not having an affair and that his marriage was fine. The polygrapher was identified to the jury only as a state officer, not as a polygraph examiner, and reportedly it is unclear from the testimony whether Peterson's alleged statement was made in the context of a polygraph exam.

Whatever the facts may be in the context of the Peterson trial, the question arises whether the public's broad awareness that polygraph results are generally inadmissible creates a trap for the unwary -- and if so, whether that's as it should be. A criminal suspect who knows that polygraph results are usually inadmissible may tend to assume that statements made during the exam cannot be used against him in any way. Yet potentially they can be. A statement later revealed to be misleading can be offered, perhaps, to show a guilty state of mind. Prosecutors might also try to charge the subject with making false statements to a law enforcement official. Should such uses of polygraph interviews be kosher? If so, should there be a requirement that polygraph subjects be warned about them, a la Miranda?