Monday 10PM Update: Passing A Polygraph, Why a Test Might Give Mixed Results
By Jillian Petrus, Reporter
EVANSDALE, Iowa - 8-year-old Elizabeth Collins and 10-year-old Lyric Cook have been missing for 11 days. Investigators believe someone abducted them from Evansdale on July 13th. The girls' bikes were found near Meyers Lake, but after days of searching, investigators will only say they have evidence to believe the girls are alive.
Misty Cook-Morrissey, Lyric’s mother, took a polygraph shortly after the girls’ disappearance. She said her first test came back ‘inconclusive’. On Sunday, Cook-Morrissey reportedly agreed to a second polygraph. On Monday, she told reporters she passed the second test.
Corporal Kurt Horch is a 21-year veteran of the Dubuque Police Department. He started giving polygraph tests four years ago.
In cases where a polygraph comes back inconclusive, Cpl. Horch says it’s most often the test-giver who makes the mistake. However, when done correctly, the detective said it is a useful tool for narrowing down your pool of suspects.
"People call it a lie detector. It's actually a fear detector,” Cpl. Horch explains. “The fear is being caught telling a lie or caught in a deception."
Cpl. Horch says about twelve years ago polygraphs went from needle and ink to fully digital. Now, the test is recorded on a computer. The software is linked to a blood pressure, respiratory and sweat gland monitors that are hooked up to the test subject.
“It’s constantly records the small physiological changes in one's body,” he says. “I always tell people it’s one of the simplest tests they're ever going to take, because we go over all the questions prior."
The examiner starts by asking what's called a control question. This is usually something pertaining to the test subjects background. An example might be, ‘Have you ever lie to someone you cared about?’
The examiner then follows with a case specific question. For example, ‘Did you help plan or participate in a house fire set on July 22nd?’
A test-giver will ask these questions multiple times in different order. The lines show when breathing, heart rate or sweat activity spikes. These measurements are all scored on a point system after the test.
"It comes down to what's the bigger threat,” Cpl. Horch says, “The guilty person is going to be worried about specific questions. An innocent person might be more nervous about background questions whether they ever lied to someone they trusted."
Horch says the polygraph is used mainly as an investigative tool. The results don't always hold up well in court, and no one can be forced to take a polygraph. The test is voluntary.
"If there's more than one suspect or viable suspects and we want to whittle that list down, we offer polygraphs to help clear your name."
The detective said a miss worded question can often cause problems with a polygraph. He add that a “super-dampening” or a traumatic event prior to the polygraph can also lead to an inconclusive result.
Polygraph examiners are required to take a 10 week course and update their training regularly. It comes out to about 400 class hours. There's actually more pressure on the test-giver to get things right.
He says it's the examiner know all the details of the case to avoid asking wrong or misleading questions.
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