At the inception of a criminal prosecution, sometimes the prosecuting authority will offer the suspect the opportunity to take a polygraph exam to “help eliminate them as a suspect”. Don’t do it! This can’t be stated strongly enough. Even though the results of a poygraph exam cannot be used against the suspect in court, admissions and confessions made during the polygraph exam or during the lead-up to the polygraph exam can be. The result of this little distinction is that the state’s prosecutors will set up the suspect’s polygraph exam with one of their polygraphers in charge. The state’s polygrapher will begin to ask preliminary questions of the suspect, while on videotape, prior to beginning the polygraph exam. These preliminary questions are ostensibly to allow the polygrapher to establish a background so that the polygrapher can best frame his or her questions during the examination. But, what the polygrapher will really do is stray into areas during this examination where he or she will start attempting to elicit incriminating reponses from the suspect. Once the polygrapher senses that he or she may have elicited an incriminating response, they’ll push on, seeking to obtain further incriminating admissions and, ultimately, a confession. Don’t forget, the admissions and a confession, can be used by the prosecution in court! Often the polygrapher will not even end up administering the polygraph exam, but will terminate the interview after eliciting the incriminating statements, or confession, or both.
So, the state administered polygraph exam is, in reality, a sham. It is nothing more than an opportunity for the state’s polygrapher to examine the suspect and obtain incriminating information. You can bet it is not a good faith effort to allow the suspect to “clear his name”.