In “Leaked Report: Drug Traffickers Obtained Classified DEA Documents from U.S. Embassy in Bogota ‘At Will,'” Bill Conroy of The Narco News Bulletin discloses a report (1.3 mb PDF) on the polygraph examination of a confidential source by DEA Special Agent E. Victor Perez. Despite widespread agreement in the polygraph community that polygraph examinations should not be conducted after extensive interrogation, Perez polygraphed the confidential source at the request of the DEA Office of Professional Responsibility (OPR) after 12 hours of interrogation by others.
At the instruction of OPR, Perez used the relatively uncommon Peak of Tension (POT) technique. According to the Federal Psychophysiological Detection of Deception Examiner Handbook:
The POT was developed by Leonarde Keeler to determine possible guilty knowledge possessed by an examinee. It is used most frequently after an examination in which a DI opinion has been rendered. The known-solution POT is used when an examinee denies any knowledge regarding a specific element of a crime or incident that has been verified through investigation or other means. The searching POT is used when the crucial key area is suspected to be known by an examinee who denies such knowledge. This format is also known as the unknown or probing POT.
The foregoing does not seem to fit the confidential source’s situation. Ultimately, Perez made a “no opinion” call, noting among other things that the examinee was “physically and mentally exhausted.”
Interestingly, Perez notes that he would have preferred to use the completely discredited Relevant/Irrelevant technique, writing “It is my opinion that with a little more information and preparation, I would have conducted a R/I testing technique vs. a POT, which could have yielded better test results by addressing more pointedly the issues to be resolved.”
The fundamental problem with polygraphy is that it just doesn’t work. Instead of relying on voodoo science to assess the truthfulness of informants, law enforcement officers should use actual investigation to confirm or disconfirm the information provided.