Eye On KELOLAND: To Tell The Truth


A lie detector became a focal point in the recent U.S. Supreme Court nomination process of Justice Brett Kavanaugh.  The woman who accused Kavanaugh of sexual assault decades ago, Christine Blasey Ford, reportedly passed a polygraph exam, placing Kavanaugh’s nomination in peril for a time.

While it’s rare for law enforcement to administer a polygraph exam to victims of sexual assault, they are used more often than you may think.  Not only as part of criminal investigations, but also for job interviews.

It takes a lot of accessories and attachments to get at the truth.

“As I put this stuff on, I just want you to relax, okay,”  Capt. Mike Walsh of the Minnehaha County Sheriff’s Dept. said.

Being hooked up to a polygraph is a lot like visiting a doctor’s office.

“The polygraph instrument is very similar to other medical devices in which it simply records what’s going on in the body,” Walsh said.

In this polygraph exam, Capt. Mike Walsh of the Minnehaha County Sheriff’s Department had me select a number. I picked two. Then he had me answer “no” to each question about my selection.

“Regarding the piece of paper on the wall, did you write the number one,” Walsh asked.

“Did you write the number five,” Walsh asked.

Then, comes the big lie.

“Did you write the number two,” Walsh asked.

It turns out, like most people, I’m not a very good liar.  My denial of writing down the number two caused the computer readout to spike. My body’s reactions gave me away.  

“So you suppressed your breathing, and it slowed your breathing down,” Walsh said.

Whenever you lie, your breathing slows, you blood pressure rises and you perspire more. The changes are small, but enough for the polygraph to detect you’re not being honest.

“That’s what a polygraph is all about, being an objective search for the truth,” Capt. Mike Walsh of the Minnehaha County Sheriff’s Dept. said.

PERRY GROTEN:  My examination, as stressful as it was, only lasted a few minutes. A typical examination lasts a couple of hours, with a lot more serious questions being asked.

“The best question is a question that is very specific and it contains an active verb. Which is, did you stab Joe? It’s not have you ever thought about stabbing anybody?  It’s completely different,” Walsh said.

A polygraph is an important tool for investigators to determine whether suspects or witnesses are being truthful. However, the results are not allowed as evidence in trials. That’s because of the human element. Not all polygraph examiners are created equal.

“Polygraphs can be screwed up, to put it very bluntly. One of the reasons why I am not a proponent for blanket admissibility for polygraph is because of the wide disparity between abilities between examiners,” Walsh said.

Sioux Falls attorney Aaron Salberg says polygraph exams are so unreliable, he tells clients not to submit to them.

“I would say, absolutely, unequivocally, not to take them. There are too many errors in the system.  They have the right to remain silent,” Salberg said.

Applicants for law enforcement jobs and sensitive government positions do have to take polygraph exams. Detective Marc Wynia had to take one as part of his screening process to join the sheriff’s department.

“There’s no surprise questions at all. It’s just everything is riding on that test, that’s what’s nerve-racking about it,” Wynia said.

While critics claim polygraphs are instruments of junk science, Walsh says they’re accurate up to 90-percent of the time. A vital piece of technology aiding law enforcement in their moment of truth.

“When we can find that piece of evidence on behalf of the investigation or on behalf of the victim and close a case out, there really is no greater feeling in the world,” Walsh said.

The Internet is full of methods claiming to beat a polygraph exam. But Walsh says they don’t work and are likely submitted by people who failed an exam. One technique calls for concealing a thumb tack and sticking yourself as you answer to throw-off the polygraph. But Walsh says a trained examiner can easily determine when a subject is reacting to pain because their body responds differently than when they’re lying.

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