Polygraph Testing in Criminal Law

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Television shows often show characters accused of a crime taking a polygraph test to prove their innocence, but in reality polygraphs are very rarely used.  There are a number of reasons that both the Defense and the prosecutor are hesitant to use polygraphs.  They can become very expensive to obtain, are very difficult to get admitted into evidence, and are not always reliable.  There are some situations in which getting a polygraph test is a good strategy, and you should consult with an experienced Defense attorney before deciding if a polygraph test would be helpful in your case.

Concerns around Polygraph Testing

Courts have always looked skeptically at the use of polygraph evidence, because it is not an exact science.  There are a number of factors that can affect the results of the test, and the interpretation of these results is subjective to the expert who is administering the test.  Polygraphs measure factors such as an individual’s heart rate, and the theory is that when an individual lies, their heart rate (among other factors) will rise.  Other things can cause this reaction, however, including the mere stress of taking a test that you feel determines your guilt or innocence.  This can create false positives, or in the alternative, an individual could prepare and rehearse for the test to make sure they don’t have any reaction even if they do lie, resulting in a false negative.  Furthermore, different analysts may come to different determinations of the results, which opens the door for the Defense and prosecution to have “dueling polygraph experts”.

To be clear, law enforcement has never been prohibited from using polygraphs to aid their investigation, but this freedom did not traditionally transfer over to the prosecutor as they determined what evidence to base their case on.   Polygraph evidence was admissible if both Defense and the prosecutor agreed to have the results admitted, but as a practical matter, the polygraph results will always favor one party and therefore the opposing party will always object.  Recently, though, courts have begun to acknowledge that as technology has developed, there are times when polygraph evidence may be reliable enough to be used in court, despite the protests of opposing counsel.

The Current Law on Polygraph Testing

The higher courts of Georgia have still not officially ruled on the admissibility of polygraphs, which leaves trial courts to rely on the rulings of federal courts.  The federal courts for Georgia’s federal circuit have ruled that even if both parties don’t agree to have polygraph evidence admitted, polygraph evidence can be used to discredit a witness’s testimony or to support and corroborate it.  There are three requirements to use polygraph evidence for these purposes: 1) the party planning to use the polygraph evidence must notify the opposing party in a timely manner, 2) the opposing party must have an opportunity to have their own polygraph test administered, and have an opportunity to challenge any disparities, and 3) the expert themselves, as well as they way in which they administered the test, must be reliable enough to be introduced into evidence under the Daubert test for reliability.  This is the most challenging part of the test for admissibility.

The Daubert analysis determines if evidence is scientifically reliable enough to admit into evidence, and has four suggested factors that courts rely on.  The factors as they would be applied to the polygraph test’s admissibility are: 1) whether the way that the test was administered and analyzed was generally accepted by the scientific community, 2) whether the techniques of the administration of the test have been peer reviewed, 3) whether the manner of administration and analysis have been tested for reliability, and 4) whether the error rate of the test is acceptably low.

It is inherently difficult for polygraph evidence to meet these marks, which means that introduction of polygraph evidence will virtually always require an intensive hearing.  Because polygraph evidence is so subjective, it is extremely difficult to nail down an exact error rate.  This means that the party hoping to introduce polygraph evidence has to make a very strong showing of the reliability in other ways, typically turning to the experience of the test administrator.  Because of this, if you are hoping to introduce polygraph evidence, you will typically have to hire an experienced and expensive administrator to perform the test in order to make sure they survive the Daubert hearing.

When Polygraph Evidence is Helpful

A Defense attorney should always be consulted when determining if you should use polygraph evidence in your case.  Polygraph evidence can sometimes be helpful for negotiating plea bargains with a prosecutor, even if the intention isn’t to get the results admitted into evidence.  Whether this will work depends on the nature of the case and of the prosecutor, however.  Some prosecutors may disregard the results entirely, while other prosecutors may be swayed by the results of the evidence to offer a more favorable plea bargain.  Your Defense attorney will be able to assess the probability of the polygraph test being helpful in your case for negotiation purposes, or if paying for one would not be the best use of your resources.

Polygraph evidence can also be extremely useful in cases that are inherently “he-said she-said”, where there is no hard evidence for the jury to consider.  In these cases, the jury’s perception of the Defendant’s honesty is usually determinative to the outcome of the case.  Using a polygraph test in these circumstances may demonstrate to the jury that between the two different stories they are hearing, yours is the one that is scientifically backed.

There is also the chance that the polygraph evidence could backfire.  If the results of the test paint you in a negative light, even if this is due to false positives, the prosecutor may then want to use your test for their case.  Therefore, deciding whether or not to invest in a polygraph test is a very delicate decision that requires the advice of an experienced Defense attorney.


If you have been charged with a crime and are considering getting a polygraph test, give Bixon Law a call today to speak to one of our experienced Georgia criminal defense lawyers. We will vigorously defend your criminal defense rights, and advocate on your behalf to have your criminal case dismissed or your charges reduced. As experienced trial attorneys, we are not afraid to take your case to trial if necessary. We represent clients in Atlanta and throughout the state of Georgia. We are lawyers who are committed to helping people in difficult situations, and we invite you to call us at 404-551-5684 for a free consultation on your case today.