Polygraph test results have doomed many a movie/book character. They proclaim their innocence, of course. They always do. And then the police hook them up to a a lie detector test and the needle draws the Sierra Nevada mountains. Then, despite alibis and witnesses to their innocence, those dang results go on to sink the main character in court. We see that scenario so often we assume that must be how it all plays out in real life.
Mmmmm, no.
Before reading further: This is not legal advice. I am not a lawyer and I sure ain’t your lawyer. I don’t even play a lawyer on TV. If your manuscript involves a courtroom setting, I highly advise you to become friends with an attorney…even though they are an attorney. 😉 I say that because a friend of mine is an attorney. Also, check out the crime section in my second Fight Write book, Fight Write: Round Two.
What the Polygraph Does
The polygraph measures three physiological responses: heart rate/blood pressure, respiration and skin conductivity. If you know what that last one means, you are way smarter than me. I had to look it up. Apparently the skin is more conductive to electricity when stimuli, internal or external, arouses the body. The idea behind these measurements is that when someone is lying, their body responds differently to that fabrication than it does the truth. And, the polygraph does its job in that respect. It does measure the body’s physiological responses in a given scenario when asked certain questions. What the polygraph does NOT do is measure deception. It also does not discriminate between physiological responses to lies and the pure stress of being in a situation where a polygraph is required. Basically a polygraph is great at testing to see if someone is uncomfortable. It can also be good at getting a confession which I will get back to.
How Is the Polygraph Test Is Administered?
The test taker will have sensors on their chest, two or three fingers and around their upper arm as for a blood pressure reading. They may have one around their forehead as well. They are then asked questions all of which must be “yes/no” in answer. The first questions are baseline. “Is your name ____?” “Are you sitting down?” The questions then become targeted to the reason for the polygraph. How quickly the questions change or how specific they are is determined by whomever wants the test done.
How Accurate Are Polygraph Tests?
The reader of the polygraph bears some weight on the accuracy/inaccuracy of the thing. The examiner has to be a person trained to sift through what is normal stress and find the body’s response to a lie. Problem with that is, the examiner is human and the test taker is human. And where there’s a human, there’s bound to be an error. I’ve seen stats that read, at best, the polygraph is right 85% of the time. At worst, 75% or less. Now, that statistic may seem pretty good until you consider that for every on hundred people sentenced found guilty by virtue of polygraph results, twenty five or more of those people were not lying.
Do You Have to Take a Polygraph Test?
You do not have to take a polygraph. Being compelled to do so in connection with a crime is actually against the U.S. Constitution and many others world-wide. In the United States, you have the right to remain silent to not incriminate yourself. Thing is, sometimes we assume that the silence is proof that something incriminating exists which just ain’t so. Sometimes law enforcement entities may ask a person to take a polygraph if for no other reason than to watch the change in that person’s behavior. And the person may take one and fail worse than I did high school Physics. But, that doesn’t mean they are guilty. Ironically, regardless of the test results, a polygraph could get an admission of guilt out of someone for the simple fact they figure the machine will catch their lies any how.
Can Polygraph Test Results Be Used in Court?
Polygraph test results are not admissible in court in the U.S. unless both parties agree to it. And, the refusal to take one should not be considered as evidence of guilt. In fact, bringing up a defendant’s refusal can cause a ruling to go to appellant court. For example, if a detective on a criminal case testifies in court, “I don’t know, the person of interest refused a polygraph,” the defense attorney should immediately object. They can even site a ruling that supports their objection. The judge would then tell the jury to disregard what was said. But, y’all, you can’t “unhear” a thing. No matter how hard a jury tries to disregard something that should not sway a decision, they are human. They may be swayed even without realizing it.
Can You Beat a Polygraph
Yes. And we will look at that in our next post! Until then, here is my favorite polygraph scene ever. If you haven’t watched Parks and Rec, you haven’t seen Chris Pratt at his finest. The test starts at the one minute mark but the whole thing is awesome. Choose the pic and it will take you to YouTube.
Until the next round at FightWrite™, get blood on your pages.
