by: Maddie Rowley

Let’s set the scene. You sit at a stainless steel table in a sterile room with three beige walls and a one-way mirror that takes up the length of the fourth wall. A single lightbulb flickers above you —on, off, on, off—like some sort of taunt; a warning that your freedom is running out. Your chest feels suffocated by the wires strapped tightly around it and your fingers look like they’re expelling strings of black, wiry web. But you’re no Spiderman. You’re not trying to save the day. You’re just trying to get away with murder. 

A man’s voice cuts through the silence. “Recreate the day of March 6th for me. What do you remember from the minute you got up to when your head hit the pillow at night?” 

The above scene sounds like it was plucked from a Mindhunter episode, right? There are lots of misconceptions about polygraphs in the true crime world, perhaps due to how they’re presented in our favorite crime shows, so I was honored (and curious) to interview former secret service agent and polygraph examiner, Mark O’Riordan, to learn more about polygraph tests and how they actually help solve cases. 

If you’d rather listen to the interview, scroll down to the bottom of the blog post.

Mark, how did you get started in your career as a polygraph examiner?

“I started applying for law enforcement jobs a little after September 11th and I wound up working for the secret service starting in 2004. Many people don’t know the secret service doesn’t just do protection but also has a pretty large investigations group. 

Around 2008, I went to the Federal Polygraph School for 16 weeks. Interviewing is actually a mixture of art and science. There are lots of psychological principles you rely on when you’re interviewing people, but there’s also a bit of intuition that comes into it and you have to know how to talk to people.

In polygraph school, you study anatomy, physiology, and psychology, and you have to understand how to use all the instruments. It’s an intensive course and very rigorous academically.”

How do polygraph tests work and what do they do?

First thing’s first: try and avoid calling polygraphs “lie detector tests” because the test doesn’t necessarily measure “lies,” it instead monitors respiration, blood volume, and electrodermal activity (EDA), which is basically measuring your skin’s sweat gland response. 

“You ask people certain questions and you look to see how their body responds,” said O’Riordan. “What you’re trying to do is to isolate responses from the autonomic nervous system which is your involuntary nervous system. We’re looking for a form of fight or flight.”

When an examiner like O’Riordan is interviewing someone (like a homicide suspect) the goal is to get the most accurate results by first understanding their medical history, their psychological history, as well as their perspective on the alleged events that pertain to the case. 

It’s also extremely important to stay unbiased throughout the interview process, which can be difficult to do. 

O’Riordan described interviewing a murder suspect in Detroit—a man who was accused of killing his girlfriend with a hammer. Within the first five minutes, O’Riordan asked “What’s your biggest concern here today?” to get rid of some of the tension in the room. 

The suspect responded, “I’m worried you won’t let me see my child when this is all done.”

“It’s pretty easy to think ‘that sounds like guilt to me,’ but you have to be unbiased,” said O’Riordan. “Even comments like that isn’t necessarily an admission to a crime. It is, what I believe, was his subconscious or an involuntary utterance of an admission of guilt, and he did end up confessing to the crime 7 ½ hours later. You have to take your time and be methodical.”

How do polygraph tests come into play inside the courtroom?

“The result of a polygraph exam isn’t evidence of a crime,” said O’Riordan. “When somebody fails the general type of polygraph exam, then it’s your job to explore why.” 

A failed polygraph exam acts as a guide for the detectives on the case to pursue new details that were uncovered during the polygraph test that can be used as evidence in court. 

How can you tell the difference between general nervousness and a lie?

“Every exam I’ve ever done, somebody’s mentioned they’re worried or nervous. I’ve taken several polygraphs myself and I was worried and nervous about them every single time. There are techniques that we use to make sure that we filter out that normal “nervousness,” said O’Riordan. 

When it comes to telling a lie, memory plays a big role in how that lie appears on the polygraph test. 

“If you shot somebody, chances are you’d have a memory of it,” said O’Riordan. “When you lie, you’re saying something that goes against your memory. Think of it as a mechanical thing—you either have to suppress a memory or alter one, which is a lot of extra work and stress on your brain, which puts you into fight or flight mode.” 

Lying is much more difficult for your brain than telling the truth is. 

Is the end-goal of a polygraph exam to elicit a confession?

O’Riordan has both exonerated homicide suspects and gotten confessions from homicide suspects throughout his years of conducting polygraph examinations. The ultimate goal of a polygraph test is to resolve the matter as best you can. 

Solving a homicide can take weeks, months, and even years, so a solid confession backed up by details that check out saves the detectives time and effort, and gives the victim’s family members the justice and closure they’re looking for in a more timely manner. 

“You have to work hard at it. You have to be ethical and smart and you have to think on your feet to make sure you’re asking the right questions and providing the best resolution that you can for the situation,” said O’Riordan.

What are some misconceptions about polygraph exams?

We normally see polygraph tests portrayed on our favorite TV shows as a guilty-looking murder suspect being peppered with questions like, “Did you shoot her with a gun?” by a polygraph examiner, but that’s not how it goes in real life. 

“The majority of a polygraph exam is just sitting across from the examiner talking to him or her. The minority of the experience is being attached to the components and having us recording your physiological responses,” said O’Riordan. 

Before every polygraph exam, the polygraph examiner reviews each and every question with the interviewee so that there are no surprises. 

“You’re trying to calm down the nervousness and we’re very methodical about it,” said O’Riordan. 

Thanks again to Mark for taking the time to answer questions about polygraph exams. Comment below and let us know if you have any questions!