Introduction

A detective calls and says:

“If you’re telling the truth, you’ll take a polygraph.”

Or maybe:

“This is your chance to clear your name.”

Many people immediately think:

“I’m innocent. Why wouldn’t I take it?”

That may be one of the biggest mistakes you can make during a criminal investigation.

The Short Answer

In most cases:

👉 No.

You should not agree to take a polygraph test without first consulting a lawyer.

In fact, many experienced criminal defense attorneys routinely advise clients against it.

What Is a Polygraph?

A polygraph is commonly called a “lie detector test.”

The machine measures things like:

• breathing
• heart rate
• blood pressure
• perspiration

The theory is that deceptive answers create physiological responses.

The problem?

Human beings are not machines.

The Biggest Misconception

People assume:

“Polygraph tests determine whether you’re lying.”

They do not.

Polygraphs measure physiological reactions.

They do not measure truth.

Why Innocent People Fail

People become nervous for many reasons:

• fear
• anxiety
• embarrassment
• stress
• confusion
• trauma

None of those things prove guilt.

Yet they may affect test results.

Why Detectives Love Polygraphs

Many people think the purpose of a polygraph is the test itself.

Often it isn’t.

The real goal is frequently the interview that occurs before, during, and after the examination.

Because people start talking.

And talking creates evidence.

The Question Nobody Asks

Imagine this:

You pass.

What happens?

Maybe nothing.

Now imagine this:

You fail.

What happens?

Suddenly investigators focus even harder on you.

The risk-reward analysis often favors silence.

Are Polygraph Results Admissible in Tennessee?

Generally speaking, polygraph results are not routinely admissible as evidence in Tennessee criminal trials.

That’s an important fact many people don’t know.

If the results are supposedly so reliable, why are they generally kept out of court?

That’s a question worth considering.

The Biggest Mistake People Make

A detective says:

“If you’ve got nothing to hide, take the test.”

People think refusal makes them look guilty.

It doesn’t.

Refusing a polygraph is not an admission of guilt.

It’s often a smart legal decision.

What You Should Do Instead

If investigators request a polygraph:

Say:

“I would like to speak with my lawyer before making any decisions.”

Then stop talking.

Why This Matters in Nashville

In Nashville and throughout

Davidson County, Tennessee

polygraphs are sometimes requested during investigations involving:

• sexual assault allegations
• theft investigations
• domestic cases
• homicide investigations
• child abuse allegations

The consequences of making the wrong decision can be enormous.

The Reality

Most people don’t get into trouble because of the machine.

They get into trouble because of what they say before and after the machine.

The Bottom Line

• Polygraphs do not directly measure truth
• Innocent people can fail
• Detectives often use polygraphs as investigative tools
• The interview surrounding the test is frequently more important than the test itself

Your safest move:

“I don’t answer questions.”

About the Author

David G. Ridings is a Nashville criminal defense attorney with almost 30 years of criminal defense experience and nearly 40 years on every side of the criminal justice system.

He is a former Metro Nashville Police Officer, former prosecutor, and has served as a Night Court Judicial Magistrate since 2023.

Known online as DrJudge, he has educated hundreds of thousands of people about their rights during police encounters and has literally written the book on the subject, “I Don’t Answer Questions.”

Call to Action

If detectives want you to take a polygraph or come in for an interview:

👉 Don’t talk. Call 1-888-DRJUDGE

The most dangerous part of a polygraph test is often everything that happens around it.