WATERLOO (KWWL) -
"We want the person to pass. We don't want them to fail,"
says polygraph examiner, Rob Duncan, a Waterloo Police Investigator and
FBI-trained polygraph examiner.
Investigator Duncan recently gave KWWL a polygraph demonstration,
as he attached numograph sensors to his lie-detector subject for the
demonstration, Waterloo Police Investigator, Jason Choppard. The numographs
monitored Jason's breathing patterns during questioning.
Duncan says, "Some
people breathe a little bit differently, so, it's watching both, like a chest
breather and an abdominal breather, and a polygraph is just something to get to
the truth."
While generally not admissible in Iowa courts, the test results can certainly
help investigators eliminate possible suspects.
"If they pass, great. They've passed the test. There shouldn't be
any problem with this person. If they fail it, then we ask them, you know, Why
did you fail. What were you thinking about when you were taking the test? And,
every once in a while, we come across somebody who's like, 'Hey, you know, I
failed because I did it.' When that happens, the admission is admissible in
court."
For the polygraph demonstration, Duncan asks, "Jason, have you ever lied to
any supervisor here at the Waterloo Police Department?"
Jason answered by asking
a question himself. "Lied, he says. No." Rob reminds him, "Just answer Yes or No,
okay?"
That's because all questions are to be answered Yes or No. Subjects are
to give no explanation whatsoever; just a Yes or No answer.
Polygraphs begin with several general questions—known as the base questions or irrelevant questions. Later, the examiner asks what are called the Bait or
Control questions; these are the questions truly relevant to the investigation.
"If they're lying, or when they're lying, their body is going to
react to it. So, basically, all a polygraph does, is it gives a reading, via
all the instruments that are hooked up to them. They say No, and they're lying.
Typically, the body is going to react to that."
But, there's is no formula in determining if a subject is telling
the truth. The results are the interpretation of the Polygraph examiner.
Polygraph exams have long been controversial. Critics of
polygraphs say the test is inherently biased against innocent individuals.
But, While the polygraph exam is generally not admissible
in court, it can be a value investigative tool for officers.
