Are polygraphs admissible in U.S. courts? A Concise Overview

The use of polygraphs in the legal system dates back to the early 20th century, when law enforcement began using them as a tool to interrogate suspects and gather information in criminal cases.

Despite their widespread use, the reliability of polygraphs was largely untested and unproven in their early days. In 1923, a New York court excluded the results of a “lie detector” test in a murder case due to the lack of scientific basis for its use.

This skepticism continued to grow throughout the mid-20th century. However, the admissibility of scientific evidence, including polygraph results, was officially established in the landmark case of Frye v. United States in 1923. The Frye decision established that scientific evidence must be generally accepted within the relevant scientific community in order to be admissible in court.

A vintage black-and-white image of a lady taking the polygraph exam

Polygraph use in court continued to be a controversial issue, with the Supreme Court ruling in 1998’s United States v. Scheffer that polygraph evidence was not admissible in court unless both the prosecution and defense agreed to its use. The Court reasoned that polygraphs were not reliable enough to be used as conclusive evidence in court and that their use could potentially prejudice a jury.

In recent years, some states have begun to reconsider the admissibility of polygraph evidence in certain circumstances. However, their use remains highly controversial, and their admissibility in court continues to be a topic of debate.

The purpose of this article is to provide you with a comprehensive understanding of the topic, Our goal is not to argue one way or another but to present you with the relevant information so that you can form your own informed opinion on the matter.


A brief overview of the US legal system

Understanding the role of polygraph evidence in the US legal system requires a basic understanding of the legal system itself. In the US, the legal system is based on the principle of adversarial litigation, where two parties present evidence and arguments to a neutral judge or jury.

Criminal cases are prosecuted by the state, with the burden of proof resting on the prosecution to prove guilt beyond a reasonable doubt. In contrast, civil cases involve disputes between private parties and often seek monetary damages.

Both criminal and civil cases follow a similar process, with the parties presenting evidence, examining witnesses, and making arguments before a judge or jury. The outcome of the case is ultimately decided by the judge or jury, based on the evidence presented.

In criminal cases, the Constitution provides several important protections for the accused, such as the right to remain silent and the right to a fair trial. In addition, the accused is presumed innocent until proven guilty, and the prosecution bears the burden of proving guilt beyond a reasonable doubt.

In civil cases, the standard of proof is lower than in criminal cases. Rather than proving guilt beyond a reasonable doubt, the plaintiff must only prove their case by a preponderance of the evidence, meaning that it is more likely than not that their claims are true.

Overall, the US legal system is a complex and multifaceted system that places a high value on the rights of the accused and the presentation of reliable evidence.


Importance of the topic

The admissibility of polygraphs in US courts is a topic of great importance for both legal professionals and the general public. Polygraph tests have been used for decades in the United States as a tool to aid in criminal investigations, and their admissibility in courtrooms has been a contentious issue.

The importance of this topic lies in the fact that polygraph tests are often used to make determinations about the guilt or innocence of an individual, and these determinations can have serious consequences. If polygraph test results are deemed admissible in court, they can be used as evidence against an individual and can sway a jury’s decision. On the other hand, if polygraph tests are deemed inadmissible, an innocent individual may be wrongfully accused and convicted.

Furthermore, the use of polygraph tests in employment and security clearance processes is also significant. Many government agencies and private companies use polygraph tests as a screening tool to determine an individual’s suitability for a job or access to classified information. The results of these tests can determine whether someone is hired, promoted, or fired.


State laws on polygraph admissibility

A blue Map of the United States

When it comes to the admissibility of polygraph evidence in the United States, it’s important to understand that the laws and regulations can vary from state to state. Currently, there are only a few states that allow polygraph evidence to be admitted in court, and even in those states, there are limitations and restrictions in place.

For example, in New Mexico, polygraph results are admissible in court if both parties agree to their use. In North Carolina, polygraph results can be used in criminal trials if certain conditions are met, such as the test being administered by a qualified expert and the results being submitted to the court in writing. In Maryland, polygraph evidence is only admissible if all parties involved agree to its use, and the results cannot be the sole basis for a conviction.

On the other hand, many states have laws explicitly prohibiting the use of polygraph evidence in court. These laws vary in scope and severity, but they generally reflect the view that polygraphs are not reliable enough to be used as evidence.

For example, in California, the results of a polygraph test are generally not admissible in criminal trials, and in most civil cases, the results can only be used if all parties involved agree to their use. In Illinois, polygraph evidence is generally not admissible in court, although there are a few exceptions.

It’s also worth noting that even in states where polygraph evidence is technically admissible, judges have significant discretion in deciding whether or not to allow it. In many cases, judges are hesitant to admit polygraph evidence because of concerns about its reliability and the potential for misuse.

In the following states, in some cases, polygraph results may be used as evidence in court:

  • Alaska
  • Colorado
  • Georgia
  • Idaho
  • Indiana
  • Kansas
  • Kentucky
  • Minnesota
  • Missouri
  • Nebraska
  • New Hampshire
  • North Dakota
  • Ohio
  • Oklahoma
  • Oregon
  • Pennsylvania
  • South Dakota
  • Tennessee
  • Texas
  • Utah
  • Virginia
  • West Virginia

In the remaining states, polygraph evidence is generally not admissible in court, although there may be some exceptions in certain circumstances.


Differences in state and federal rules regarding admissibility

At the federal level, the admissibility of polygraph results is governed by the Federal Rules of Evidence. According to Rule 702, expert testimony is admissible if it will assist the trier of fact, the witness is qualified as an expert, the testimony is based on reliable methodology, and the testimony is relevant to the case at hand. However, in the case of polygraph results, the rule specifically excludes evidence based on a polygraph test.

In contrast, some states have their own rules regarding the admissibility of polygraph results. As previously mentioned, there are currently 19 states that allow polygraph evidence in certain circumstances. However, the specific requirements for admissibility can vary widely between states. For example, in Texas, polygraph evidence is admissible only if both parties agree to its use, while in New Mexico, polygraph evidence is admissible in certain criminal cases only if the defendant agrees to take the test and the prosecution agrees to the admission of the results.

It’s also worth noting that even in states where polygraph evidence is admissible, there may be limitations on how it can be used. For example, in California, polygraph evidence is admissible only for impeachment purposes, which means it can be used to challenge the credibility of a witness but not as substantive evidence to prove or disprove a particular fact in the case.


How judges determine admissibility

When judges are faced with the decision of whether to admit or exclude evidence obtained through a polygraph, there are a number of factors they take into account. While the specific rules and standards may vary depending on the jurisdiction, there are some common considerations that judges will typically take into account.

One of the primary factors that judges will consider is the reliability of the polygraph as a tool for detecting deception. In general, judges will be hesitant to admit polygraph evidence if they believe that it is not a reliable indicator of whether someone is telling the truth. To make this determination, they may consider scientific studies, expert testimony, and the results of previous cases in which polygraph evidence was admitted or excluded.

Another important factor is whether the polygraph was administered in a way that is considered fair and accurate. For example, judges may consider whether the person being tested was given clear instructions, whether the examiner was properly trained and certified, and whether the test was conducted in an appropriate setting. If the judge determines that the polygraph was not administered fairly or accurately, this can be grounds for excluding the evidence.

Judges will also consider the potential impact that admitting polygraph evidence may have on the fairness of the trial or the rights of the defendant. For example, if admitting the evidence would be unfairly prejudicial to the defendant or would violate their right against self-incrimination, the judge may exclude it.

Ultimately, judges have a great deal of discretion when it comes to determining the admissibility of polygraph evidence. While there are some general standards and guidelines that they will consider, the decision will ultimately depend on the specific facts and circumstances of each case.


The use of polygraphs in plea bargaining and pretrial negotiations

a polygraph test administered to a subject by an investigator.

When it comes to criminal cases, plea bargaining and pretrial negotiations can often be key components of the legal process. In some instances, polygraph examinations may be used as a tool in these negotiations.

Even though polygraph examinations are generally not admissible in court as evidence, that does not mean they are never used in legal proceedings. In plea bargaining and pretrial negotiations, polygraph examinations may be used to persuade a prosecutor or defense attorney to accept or reject a plea deal.

The use of polygraphs in these negotiations can be controversial, as the results of a polygraph examination are not 100% accurate. Moreover, the use of polygraph examinations in this context raises ethical concerns, as a defendant may be pressured to take a polygraph examination, even though it is not legally required.

Some jurisdictions have explicit rules regarding the use of polygraphs in plea bargaining and pretrial negotiations. For example, in California, the use of polygraph examinations in these negotiations is generally prohibited. Other jurisdictions do not have specific rules, leaving it up to the discretion of the parties involved.

In some cases, polygraph examinations may be used as a bargaining tool. For example, a defendant who passes a polygraph examination may be more likely to receive a favorable plea deal. Conversely, a defendant who fails a polygraph examination may be more likely to accept a less favorable plea deal.


Recent developments in the use of polygraphs in US courts

While some states continue to ban the use of polygraph evidence, others have implemented more lenient standards that permit their use under certain circumstances.

In 2013, the American Polygraph Association released new guidelines for the use of polygraphs in criminal investigations, which recommended that only trained examiners administer the tests and that their results should not be the sole basis for making decisions about a suspect’s guilt or innocence.

Some recent court cases have upheld the admissibility of polygraph evidence under certain circumstances. For example, in the 2015 case of US v. Miller, the Fourth Circuit Court of Appeals ruled that polygraph evidence could be admissible in certain instances, such as when it is used to corroborate other evidence. Similarly, in 2020, the Ninth Circuit Court of Appeals held in US v. Nickerson that a defendant could offer polygraph results to support a claim of innocence.

However, not all recent developments have been in favor of the use of polygraphs. In 2019, the New Jersey Supreme Court issued a ruling that tightened restrictions on the use of polygraph evidence in criminal cases, requiring prosecutors to meet strict requirements before the results of a polygraph could be admitted in court. The court found that the use of polygraph evidence in the absence of a clear legal framework was inappropriate.


When are polygraphs admissible in court?

While the examiner watches the screen, a polygraph examinee is attached to the device.

The conditions under which test results can be used as evidence vary by state. However, the following are some frequent circumstances that may make it necessary for the results to be accepted in court:

  • In certain states, results must be agreed upon by both the prosecution and the defense before they may be entered as evidence.
  • A trained specialist administered the polygraph. The tests must be performed by a competent and licensed polygraph examiner who can vouch for the accuracy of the results.
  • The results were obtained in accordance with recognized standards. Polygraphs must be conducted in some states in accordance with recognized criteria, such as those provided by the American Polygraph Association.


In some states, polygraph results can only be used as supporting evidence and not as the main reason for a conviction. The findings are only utilized in certain sorts of cases.

It is crucial to note that these are only some of the requirements that may be necessary for polygraph evidence to be admissible in court and that state rules and regulations can vary and change.


Why are polygraphs not admissible in court, generally?

Firstly, there is the issue of reliability. There are a number of factors that can influence the results of a polygraph test, including the skill of the examiner, the mental and emotional state of the person being tested, and even the wording of the questions being asked. This means that there is no guarantee that a polygraph test will accurately determine whether someone is telling the truth, which makes it difficult to rely on as evidence in court.

Another issue is validity. Polygraph exams measure physiological responses, such as heart rate, blood pressure, and respiration, which are believed to indicate deception. However, these responses can be affected by a range of factors, including anxiety, fear, and physical discomfort, which may not necessarily be related to lying.

In addition to these concerns about reliability and validity, there are also worries about the potential for prejudice against the defendant. If a jury were to hear that a defendant had failed a polygraph test, they may be more likely to assume that the defendant is guilty, even if the test results were not reliable or valid.

Lastly, there are also ethical and legal concerns surrounding the use of polygraphs in court. In many cases, the use of polygraphs has been seen as a violation of the Fifth Amendment, which protects individuals from self-incrimination. This is because polygraphs are often used to try to get people to confess to crimes or other wrongdoing, which could be seen as a form of self-incrimination. Additionally, some people argue that the use of polygraphs is a violation of privacy as it involves measuring physiological responses.


Admissibility in other countries’ courts

When it comes to the admissibility of polygraph evidence in other countries’ courts, the laws remain fairly similar to those in the US.

In Canada, for example, polygraph evidence is generally not admissible in court. However, there are some exceptions, such as when the evidence is offered to rebut a charge of lying or when it is used in severe cases. In these cases, the polygraph evidence must meet strict standards of reliability and accuracy.

In the United Kingdom, polygraph evidence is not admissible in criminal trials, but it may be used in some other contexts, such as employment disputes or some civil cases.

Australia has a similar approach, with polygraph evidence generally not admissible in criminal trials, but potentially admissible in other contexts. However, as in other countries, the admissibility of such evidence depends on its reliability and accuracy.

In some countries, such as Israel, polygraph evidence is slightly more accepted in court. In Israel, for example, a polygraph exam can be used as part of the pre-trial process, and the results may be admitted as evidence if both parties agree to their admissibility.



In conclusion, polygraph tests have been a controversial topic in the legal system for many years. While they can be used as an investigative tool, their admissibility in court is limited in most jurisdictions.

As we have seen, polygraphs work by measuring physiological responses that can indicate deception and are generally accurate, but these responses can also be triggered by other factors such as anxiety or stress, leading to false positives or false negatives. Moreover, polygraph examiners are not infallible, and their interpretation of the results can be influenced by subjective factors such as bias or preconceptions.

It is important to note that the admissibility of polygraph tests varies by jurisdiction and may be subject to change. As technology and testing methods improve, it is possible that the use of polygraphs in legal proceedings may become more widely accepted.

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