Lie Detectors

[xoxoxoBruce]

If you have to face one they can be beaten. Doug Williams was sent to jail for teaching people how.

As an examiner, Williams saw the polygraph simply as a prop to scare confessions out of suspects, “a psychological billy club.” And over time, he came to believe that a properly trained subject could game the machine. The key realization occurred when a friend on the force came into the station describing a high-speed chase from the night before. With all the fear and adrenaline, he told Williams, the “pucker factor” had been high—he’d been “pinching doughnuts” out of the seat of his patrol car.
That vivid image made Williams wonder if the same process could run in reverse, if an intentional “pucker” could trigger the physiological stress responses a polygraph traced. That would allow a subject to manipulate his response to the control questions and rig the test. For a lark, Williams hooked himself up to the machine in his office and clenched. “Lo and behold,” he recalls, “the most beautiful blood pressure increase you ever saw, accompanied by a corresponding increase in sweat activity in my hand.” The effect was even more convincing if he simultaneously altered his breathing pattern to fool the pneumographs.

[Big Sarge]

Don't forget, I was a forensic psychophysiologist for several years. My internship was with the Mississippi Bureau of Investigations. I also ran a few exams in Karbala during OIF III.

With an analog instrument, it is possible to "sway" an examiner who has become complacent because he relies on on manual scoring. His errors are usually founded when the charts are reviewed for quality control. I have a digital instrument. We run 3 scoring algorithms plus a manual score. All must be in agreement as to the scoring. At the very best, a person using extremely advance countermeasures will score an inconclusive and trigger a re-exam. The latest polygraph technology uses infrared sensors for detection of heat changes in the face. Also, the penile response gauge is finally gaining acceptance in the US despite it's use for over two decades by other countries. I don't see how anyone could teach countermeasures to these.

Polygraphs are primarily used for single scope and dual scope investigations of security clearances and sexual offender post release examination, at least in my area. Many of the larger law enforcement agencies use polygraph exams as a pre-employment screening tool.

In God we trust, all other we polygraph.

[Gravdigr]

Barney Miller episode "Voice Analyzer"



Pertinent parts start @ 10:15, and again @ 20:10.