Chapter 19: Employing Polygraph Assessment

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So, if you are listening to this right now, chances are you are a college student staring down a massive forensic psychology exam.

Right.

Just wondering how you are going to memorize literally everything before tomorrow.

Yeah, exactly.

Take a deep breath.

We have got you covered.

Think of us as like your personal tutors.

Our mission today is to completely demystify chapter 19 of the Handbook of Forensic Psychology, fourth edition.

The one titled, Employing Polygraph Assessment.

Yeah, that one.

Oh.

And we are going to walk you through everything you need to know.

I mean, from the actual physical wires on the instrument itself to the, you know, the high stakes legal battles that dictate how it's used in a courtroom.

Because, well, millions of these tests are given every year, right?

Yet the scientific community is just incredibly skeptical of them.

Oh, completely.

So why is a tool that research psychologists almost universally distrust still an absolute cornerstone of our justice and national security systems?

It's a massive paradox.

And to make sense of it, you really have to look at the sheer scale of how these instruments are deployed today.

I mean, tens of thousands of polygraph tests are administered annually in the U .S.

alone.

Tens of thousands.

Yeah.

But it's funny because back in 1988, there was this thing called the Employee Polygraph Protection Act, or EPA.

Yeah.

And it essentially banned most private employers from using polygraphs to screen job applicants.

Right.

So, like, you can't be forced to take a polygraph to get a job at a retail store or a restaurant.

Exactly.

But the government, well, they exempted themselves from that rule.

So as a result, these tests are heavily utilized for government security clearances, especially in a post -9 -11 world at high security facilities, like nuclear weapons laboratories.

And beyond government clearance, I mean, they are heavily used by police in criminal investigations.

Plus, we see them pop up in family courts during custody battles, and they're a total staple in sex offender treatment programs.

Right.

To make sure offenders aren't hiding past crimes.

Yeah.

But the chapter points out this glaring disconnect regarding the people actually running the tests.

Like, the polygrapher is administering these exams.

They are generally not psychologists.

No, not at all.

They're mostly trained at facilities like the National Center for Credibility Assessment, the NCCA.

Which is run by the Department of Defense, right?

Yep.

They get this intensive hands -on training in operating the equipment and conducting interviews.

But their profession operates, well, it's largely independent from mainstream psychological science.

Which is a major issue when you look at the physical instrument itself.

A really great analogy to keep in mind exam is that a polygraph is basically just an extremely sensitive fitness tracker.

I love that analogy.

It's so true.

Right.

It is not a magical Pinocchio nose detector.

It does not measure lying.

It only measures bodily arousal.

Right.

If you picture someone taking the test, they had these expandable pneumatic belts wrapped tightly around their chest and stomach.

To measure breathing patterns, right.

Exactly.

And then they have skin conductance electrodes attached to their fingertips.

That's to measure sweat, which the book refers to as the galvanic skin response.

And the standard blood pressure cuff squeezed around their arm to track heart rate.

Yeah.

Cardiovascular activity.

And that is literally all the machine does.

There is absolutely no unique physiological response that happens only when a human being tells a lie.

So because it only tracks physiological arousal, sweat, breathing, heart rate, the entire success of the test hinges on psychological manipulation.

Yes.

How the examiner asks the questions is everything.

The instrument is just a recording device.

The real test is the interrogation playbook.

And the most common technique you need to know for criminal cases is the control question technique, the CQT.

Yeah, the CQT.

It follows a very specific, highly structured procedure.

It starts with a pre -test interview, which includes something called a STEM test.

The STEM test.

That's where they have you pick a number out of a deck of cards, right?

Right.

And then they run the machine to prove they can catch you lying about which number you picked.

The psychological goal here is to convince the subject that the machine is just absolutely infallible.

And once they believe that the actual test begins, it mixes relevant questions with control questions.

Yes.

The relevant question directly addresses the crime.

Like, did you shoot the victim?

And the control question is something broad and uncomfortable about your general character.

Like,

before age 24, did you ever hurt someone you loved?

Exactly.

Then the examiner takes the physiological data from those questions and numerically scores the responses.

The scale goes from minus five, indicating deception, to plus five, indicating truthfulness.

But the actual score is often just the stepping stone, isn't it?

Oh, totally.

The ultimate goal of the CQT is the post -disinterrogation.

When someone shows deception on the charts, the examiner uses those failed results as leverage to just pressure the subject into a confession.

The machine is basically a prop.

A very intimidating prop to break down defenses.

Wait, hang on.

Let me just put myself in that chair for a second.

Let's say I'm totally innocent.

But a detective hooks me up to a machine with wires everywhere, looks me dead in the eye, and asks,

did you murder this person?

Yeah.

My heart is going to pound out of my chest.

I'm going to start sweating simply because my life is on the line.

How does the And that reaction right there is the foundational criticism of the entire CQT process.

Polygraphers are acutely aware of this problem.

So how do they deal with it?

Well, to counter it, the examiner has to actively manipulate the subject's psychological set during the pre -test interview.

They have to make the control question, have you ever hurt someone you loved, feel like the most dangerous question in the room.

Oh, I see.

Yeah.

The examiner implies that if you show deception on that broad character question, you'll be deemed a fundamentally dishonest person.

Yeah.

And therefore, they'll just assume you were guilty of the murder.

Wow.

So the whole strategy relies on making an innocent person more terrified of the vague control question than the relevant question about an actual murder.

Exactly.

It really underscores just how inherently subjective and manipulative the procedure is.

That's wild.

Okay.

Another variant of this that you will need for your exam is the directed lie technique or DLT.

Yeah, the DLT.

It operates similarly to the CQT.

But instead of using vague control questions to create anxiety, the subject is explicitly instructed to lie to certain questions.

Like the examiner might say, I'm going to ask if you have ever made a mistake and I want you to lie and say no.

Right.

The idea is to establish a clear physiological baseline of what the person's body does when they lie on purpose to compare against the relevant crime questions.

But the most scientifically supported alternative takes a completely different approach.

It's the built -in knowledge test or GKT, also called the concealed information test.

Yes.

Instead of asking direct questions like, did you do it, the GKT functions as a multiple -choice memory test looking for hidden details of the crime.

So the examiner would ask, was the victim killed with a pipe, a bat,

a hammer,

a knife?

Exactly.

And the math behind the GKT is just fascinating.

Yeah.

An innocent person who has no idea how the crime was committed has a one in five chance of randomly reacting to the correct weapon.

But if the examiner asks 10 of these multiple -choice questions,

the odds of an innocent person accidentally showing their strongest physiological reaction to all 10 correct keys is like one in 10 million.

Right.

It completely reframes the process.

It isn't testing deception at all.

It's testing memory recognition.

That makes so much more sense.

But for personnel screening, like those background checks for government jobs we mentioned earlier, the approach changes again, right?

Yeah.

They rely on the relevant irrelevant technique or RIT and the test for espionage and sabotage, the TES.

And those use sweeping, generalized questions about drug use, divided loyalties, or past security violations interspersed with completely innocuous questions.

Which is why the scientific community is highly critical of these screening methods.

Because unlike a specific criminal investigation, they are essentially wide net fishing expeditions.

There's no specific incident to anchor the physiological responses to.

Okay.

So knowing how these questions are structured brings us to the massive scientific hurdle outlined in the chapter.

Do these psychological manipulations actually produce valid, reliable results?

To understand that debate for the exam, you have to grasp the difference between lab studies and field studies.

Right.

Lab studies typically involve college students committing mock crimes, like stealing 20 bucks from a desk in a controlled environment.

Which is fun, but the problem is that these studies drastically overestimate the accuracy of the polygraph.

Because a student in a lab simply does not experience the real world visceral terror of potentially going to prison for the rest of their life.

The stakes are completely artificial.

Right.

Field studies attempt to solve that by looking at real police cases.

But they introduce an entirely different flaw known as the confession bias.

The confession bias.

Yeah.

In a field study, researchers need to know for sure who was actually guilty and who was actually innocent to grade the polygraph's accuracy.

Right.

The ground truth.

Exactly.

And usually the only way examiners can verify their test results with absolute certainty is when they secure a post -test confession.

But you only get a confession when someone fails the test and gets interrogated.

You nailed it.

Therefore, the studies look artificially perfect.

They completely ignore all the innocent people who might have falsely failed the test because those people deny the crime and never confess.

So their cases are just excluded from the data set.

Wow.

So to get around that confession bias, the authors of the chapter highlight a crucial piece of research called the Royal Canadian Mounted Police Study.

The RCMP study.

Very important study.

The researchers went out of their way to find ground truth independent of confessions using DNA or other concrete evidence.

And when they looked at the real world data, they found that the control question technique's accuracy for innocent people was only 57%.

57%.

That is barely better than a coin flip.

It is.

And on top of that staggering false positive rate,

the CQT is incredibly vulnerable to countermeasures.

Right.

Countermeasures.

Studies repeatedly demonstrate that guilty individuals can easily beat the CQT by intentionally spiking their own heart rate or sweat production during the control questions.

Because if you artificially boost your body's reaction to the control questions,

your reaction to the relevant crime questions looks tame by comparison, and you pass.

And subjects do this using simple physical actions like biting the side of their tongue or pressing their toes into the floor, or even mental countermeasures like counting backwards by sevens in their head.

And the research show that experienced examiners couldn't even tell the subjects were employing these techniques.

Okay, so if the CQT is essentially a coin flip for innocent people, and you can beat it by biting your tongue, why not just use the guilty knowledge test?

I mean, we just talked about how it has a one in 10 million error rate if you ask enough questions.

The chapter itself states the GKT is 88 to 97 % accurate.

I know, it's frustrating.

The reluctance to adopt the GKT comes down to practical limitations in police work and just deep -seated institutional stubbornness.

Oh, of course.

North American examiners largely refuse to use the GKT for three main reasons.

First, many simply believe the CQT is already highly accurate and don't see a reason to change.

Second, the GKT requires law enforcement to keep specific, vivid details of the crime completely out of the media so that only the true perpetrator would recognize them.

And in the age of social media and 24 -hour news, preventing leaks is basically impossible.

Exactly.

And third, the GKT does not easily facilitate confessions.

It is an objective test of memory, whereas the CQT is designed to create the psychological pressure needed to make a suspect break down and confess, which is the ultimate goal of most police interrogations.

Right, it's about the confession.

So the 2003 National Research Council report, the NRC report, synthesized all of this conflicting data.

That's a key document for the exam.

Yes.

The council concluded that specific incident testing, like a criminal investigation, is, quote, better than chance, but still scientifically flawed.

And more alarmingly, they concluded that sweeping screening tests are essentially phishing expeditions with dangerously high false negative rates, meaning actual spies or security threats could easily pass them undetected.

Because traditional polygraphs rely on scientifically muddy measures like sweat and heart rate, researchers have spent decades searching for high -tech alternatives to meet modern legal standards.

The focus has really shifted from measuring peripheral nervous system reactions to looking directly at the brain.

And the first major alternative discussed in the chapter is ERP, or event -related potentials, specifically focusing on the P300 brain wave.

Right.

The P300 is a specific electrical wave in the brain that spikes involuntarily when a person recognizes something rare and highly significant.

So researchers essentially turned this into a high -tech version of the guilty knowledge test.

You place sensors on a suspect's scalp and flash images of the crime scene on a computer screen.

An innocent person's brain processes the images as random and does nothing.

But a guilty person's brain recognizes the specific murder weapon and their P300 wave spikes automatically.

They can't control it.

And this specific technology actually made its way into the courtroom.

The exam will likely ask about Harrington v.

State of Iowa.

In this case, a man convicted of murder took a P300 -based test years after his conviction.

The results showed that his brain did not exhibit a P300 spike in response to key, unpublicized details of the crime scene.

But his brain did show recognition when shown details of his alibi.

And the Iowa Supreme Court actually allowed this evidence to be heard.

And it contributed to overturning his conviction.

It did.

The specific method used in that case was a patented technique called murmur, developed by a researcher named Lawrence Farwell.

However, the chapter points out intense scientific pushback against Farwell's murmur technique.

And it's easy to see why researchers push back.

Farwell patented the specific mathematical algorithms he uses to score the murmur results.

He treats it like proprietary business software.

It's like trying to treat a scientific, peer -reviewed process, like the secret recipe for Coca -Cola.

You can't just walk into a courtroom where someone's life is on the line and say, my brain machine works perfectly, but I won't let independent scientists see the math to verify how it works.

That completely undermines the scientific method.

Absolutely.

Furthermore,

independent research demonstrated that the same physical and mental countermeasures that defeat the traditional polygraph can still beat these brain tests.

Really?

Yeah.

If a guilty suspect performs mental gymnastics, like silently counting or focusing intensely, every time an irrelevant picture flashes on the screen, it creates artificial spikes that mess up the baseline reading.

Oh, wow.

To combat this, researchers created the complex trial protocol.

It's an updated testing method designed to outsmart those countermeasures.

The technology is advancing, but it remains a constant cat and mouse game between test designers and deceptive subjects.

The chapter also covers neuroimaging, specifically fMRI, which tracks blood flow in the brain.

The theory behind fMRI lie detection is that lying is cognitively more demanding than telling the truth.

Right.

It takes more brain power to invent a lie and suppress the truth.

So the prefrontal cortex, the area of the brain handling complex planning, requires more oxygenated blood, which lights up on the scanner.

But the chapter issues a massive warning about applying basic laboratory fMRI studies to real world criminal suspects.

If your brain lights up during an fMRI interrogation, it might not be because you are expending cognitive effort to lie.

It might simply be because the question did you kill her induces absolute terror.

The scanner measures brain activity, not the specific intent of deception.

Right.

And the text briefly touches on a few other alternative technologies you should be aware of.

Thermal imaging uses specialized cameras, sometimes deployed at airports, to detect changes in facial blood flow that occur when someone is stressed.

But studies show that trained human interviewers actually scored better at detecting deception than the expensive thermal cameras.

Yeah.

And finally, there is voice stress analysis, which claims to detect micro tremors in the voice when someone lies.

The chapter is unequivocal on this point.

Voice stress analysis has zero scientific backing.

None at all.

It performs at chance levels and is widely considered by the scientific community to be practically pseudoscience.

So with all this fierce debate over P300 brainwaves, hidden algorithms, fMRI blood flow, and traditional sweat tests, how does a judge decide what a jury is actually allowed to see?

This is where the chapter shifts from clinical validity to legal admissibility.

How does a polygraph actually get introduced as evidence in court?

Well, there are generally two primary routes.

The first is a stipulated test.

This occurs when both the prosecution and the defense agree beforehand that the results of the polygraph will be admissible in court, regardless of whether the defendant passes or fails.

And the second route is a friendly test.

This happens when a defense attorney secretly hires a private polygraph examiner to test their client.

The strategy behind a friendly test is entirely about risk management.

Because the test is secret, the client has no fear of failing.

If they fail, attorney -client privilege protects the results, and the lawyer simply throws the report in the trash.

The prosecution never even finds out.

Exactly.

But if the client passes, the defense attorney will attempt to introduce those passing results into evidence to prove their client's innocence.

Which brings us to the critical case law you absolutely must know for your exam.

Historically, the standard for admitting any scientific evidence into a courtroom was based on Frey v.

United States from 1923.

Right.

The Frey standard requires that a scientific technique have general acceptance within its relevant scientific community.

Because polygraphs have never enjoyed general acceptance among psychologists, they were historically banned from courtrooms under the Frey rule.

But the landscape shifted in 1993 with the Supreme Court case Daubert v.

Merrill Dow Pharmaceuticals.

The Daubert standard is more flexible and is used in federal courts and many state courts today.

Instead of just looking for general acceptance, Daubert asks judges to act as gatekeepers.

They have to evaluate whether the technique has been peer reviewed, whether it is known and acceptable error rates, and whether it has underlying scientific validity.

Even under the more flexible Daubert standard,

though, polygraph evidence consistently struggles to make it into court.

This ongoing legal friction was highlighted in the 1998 Supreme Court case United States v.

Scheffer.

In Scheffer, the Supreme Court ruled that military courts are completely justified in banning polygraph evidence entirely.

The court's reasoning was straightforward.

There is simply no consensus in the scientific community that polygraph testing is a scientifically valid measure of truthfulness.

And judges aren't just looking at the science.

They are heavily influenced by rule 403 of the federal rules of evidence.

Yes.

Rule 403 allows a judge to exclude evidence if its potential to prejudice or confuse a jury outweighs its actual value.

Because judges are terrified of the scientific aura of a polygraph machine.

They worry that if a jury sees a machine pumping out a chart that says deceptive, the jury will blindly follow the machine and stop doing their actual constitutional job, which is to weigh the evidence and decide guilt or innocence themselves.

This tension highlights the most crucial distinction in the entire chapter.

The difference between legal and clinical standards.

A tool can have immense investigative utility for law enforcement.

A detective might use a failed polygraph to brainstorm new leads, narrow down a suspect list, or push a suspect until they confess.

But that exact same tool completely fails the Daubert standard for scientific reliability, which is the high rigorous bar required when you are using evidence to take away someone's freedom in a court of law.

Utility does not equal validity.

Exactly.

So to summarize the grand irony of chapter 19 and synthesize all of this for your exam tomorrow.

The ultimate takeaway is this.

Major scientific bodies, including the American Psychological Association and the Society for Psychophysiological Research, overwhelmingly reject the control question technique.

They do not believe it is a scientifically sound method for detecting deception.

Though they do respect the scientific foundation of the guilty knowledge test.

Yes, they do.

Yet the CQT survives and continues to be the dominant method used by law enforcement because of its immense utility.

The CQT acts as a bogus pipeline.

A bogus pipeline.

It is a highly effective, intimidating theatrical prop.

The wires, the charts, and the pretest manipulation successfully scare suspects,

government employees, and sex offenders into telling the truth or confessing to crimes.

It works incredibly well as an interrogation tool, even if it fails completely as a scientific instrument.

The machine might not actually know when you are lying, but the person running it knows exactly how to make you tell the truth anyway.

Exactly.

On behalf of the last minute lecture team, I want to give a warm thank you for joining this deep dive into the source material.

Good luck on your forensic psychology exam tomorrow.

We know you are going to crush it.

Absolutely.

Good luck.

But before you log off and go study your flashcards, I want to leave you with one final thought to mull over based on the text.

The chapter mentions researchers are frantically trying to perfect fMRI brain scan lie detectors to finally get them admitted into court under the Do scientists ever actually achieve 100 % accuracy with a brain scanner?

What happens to the Fifth Amendment right against self -incrimination?

If your mouth stays completely shut but your prefrontal cortex lights up on a screen for the jury to see, is your own mind testifying against you?