Are Polygraphs Admissible In Court? And Other Common Questions

Have you ever noticed that the media loves to use a lie detector test to help prove criminal charges?

I wanted to know are polygraphs admissible in court?

Turns out polygraph admissibility is questionable. We'll discuss what a polygraph is inadmissible in court most of the time, how accurate is a lie detector test, how polygraphs work, the states that allow polygraph evidence, and how much a private lie detector session costs (It's not cheap).

Disclaimer

Nothing is this blog is legal advice. I am not a licensed attorney in any state and therefore cannot provide legal advice. It is imply for informational purposes only. Please find a licensed attorney if you are being asked to take a polygraph or defend yourself in either criminal or civil cases.

Are polygraphs admissible in court?

Not polygraphs are not normally admissible in court in the United States. In the 1998 case United States v. Scheffer the U.S. Supreme Court’ ruled that the exclusion of polygraph results does not violate a defendant’s constitutional rights. The Court cited polygraph accuracy and the risk of removing the jury’s role from a trial.

This ruling made it where lower courts have the right to ban polygraph evidence, but specified some scenarios where a polygraph examination may be admitted including:

1. When both parties agree to admit the results of the lie detector test.

2. When evaluating bail and sentencing.

3. When revoking probation or supervised release

   
   

How accurate is a polygraph test?

75%-87%. A polygraph test is not accurate enough to be confident in their result beyond a shadow of a doubt. According to the American Polygraph Association the tests are 87% effective, but independent research from the 2003 National Academy of Sciences found a polygraph examination is only 75% accurate.

The NAS study was reviewed in 2018 and came to the same conclusion about polygraph tests.

In other words, lie detector tests provide the wrong conclusion one out of every four to eight times. Would you want to risk your life on that? I wouldn't.

How do lie detector tests work?

According to Cornell Law School lie detector tests work by testing your blood pressure, heart rate, perspiration, respiration, and skin conductivity. Polygraph tests are effectively more advanced EKGs that the polygraph administrator hooks up to you.

Then they ask a series of questions to test how truthful you are being. They start with simple questions like your name, birthday, and information most people wouldn't lie about.

If you lie during the baseline questions, it can throw off detection of a lie. Plus the way they use a polygraph test means that it picks up anxiety and other conditions that may have nothing to do with the truth.

In other words, the likelihood of false positives is higher than a false negative. That's counter-intuitive to innocent until proven guilty.

Should I take a polygraph examination?

NO! Don't take a polygraph test unless your criminal defense attorneys recommend it. (Once again this is not legal advice because I'm not licensed to practice law. Seek legal advice from an attorney. If you are an attorney, reach out if you need help with content).

You can take a private polygraph test if your attorney believes it can help you get a charge dropped or a better plea bargain, but make sure the polygraph exam is conducted in a way where it can not be brought to court unless the test results show you are telling the truth.

A polygraph test could make or break your case depending on the results. Given both the defense and the prosecution's careers benefit from winning the case, I have a hard time imagining why either would want to allow lie detector tests as evidence in the court room.

In addition, they take time and cost money, which our governments don't need to be wasting.

Polygraph FAQs

Are polygraphs admissible in civil court?

Sometimes. Polygraphs are not normally allowed as evidence in civil court because there is concern about the polygraph test accuracy. Test results are admissible assuming there are no laws prohibiting lie detector tests in your state,both sides agree to the use of the polygraph results, and the judge allows it.

From a practicality standpoint, do you really want to spend money on a polygraph test that may give a false positive?

What states are polygraphs admissible in court?

According to Law Info.com the states that allow polygraph tests as evidence in a criminal case include Alabama, Arkansas, Delaware, Idaho, Indiana, Iowa, Kansas, New Jersey, New Mexico, North Dakota, Ohio, Utah, Washington, and Wyoming.

In addition, the following states allow a polygraph as evidence in a court proceeding in some scenarios or when both parties approve: Arizona, California, Florida, Georgia, and Nevada.

Can someone pass a lie detector test and still be guilty?

Yes. Someone can pass a lie detector test and still be guilty. The polygraph machine only detects you vitals like blood pressure and heart rate to help the polygraph examiner detect whether you are lying.

Compulsive liars, psychopaths, sociopaths, and others may be able to pass a polygraph test because they tend to have different physiological responses to the examination.

How much are lie detector tests?

$200 to $2,000. According to Shouse Law lie detector tests cost between $200 and $800 for a 2-hour session, while all day with a polygraph examiner and polygraph machine may cost up to $2,000.

Closing

While the media likes to portray polygraph results as something that is routinely used by law enforcement, prosecution, and criminal defense lawyers, the Supreme Court ruled that polygraphs are allowed to be ruled inadmissible in court under most scenarios.

The Supreme Court listed several factors that led them to draw the conclusion including inaccuracy and whether it impacted the role of the jury in a trial. Given only about at 75% accuracy of polygraph machines and the test results might not be admissible evidence during a trial, it makes me question why police or prosecution would even bother questioning someone while using one.

While detecting blood pressure and heart rate can be useful information about whether a suspect is telling the true, there are plenty of reasons why a witness or suspect might have those symptoms besides they aren't telling the truth.

In addition the number of state courts that allow evidence from a polygraph lie detector are low enough that I am kind surprised that there's a whole industry organization for the operators of lie detectors.