Polygraph examinations, often called lie detector tests, appear frequently in military investigations. A service member may be asked to take one during a criminal inquiry, or may want to introduce a favorable result to support a claim of innocence. The rules governing whether those results can be used at trial are strict. This article explains the central limitation on polygraph evidence in a military court-martial and the practical realities that flow from it.
The governing rule: Military Rule of Evidence 707
The use of polygraph results at a court-martial is controlled by Military Rule of Evidence 707. The rule provides a categorical bar: the results of a polygraph examination, the opinion of a polygraph examiner, or any reference to an offer to take, failure to take, or taking of a polygraph examination is not admissible at trial. This is a per se rule of exclusion. It does not call for a case-by-case weighing of how reliable a particular examination was. The evidence is simply not admitted.
The breadth of the rule is important. It reaches not only the raw “pass” or “fail” charts but also the examiner’s opinion about truthfulness and even references to the fact that an examination was offered or taken. That means neither side can ordinarily tell the panel that the accused passed a polygraph, failed one, agreed to take one, or refused one.
The Supreme Court upheld the rule in United States v. Scheffer
The constitutionality of this categorical exclusion was settled by the Supreme Court in United States v. Scheffer, 523 U.S. 303 (1998). In that case, an airman took a polygraph examination that indicated no deception when he denied using drugs, but a urinalysis later showed methamphetamine. The military judge relied on Military Rule of Evidence 707 to exclude the favorable polygraph result. The accused argued that excluding evidence supporting his defense violated his Sixth Amendment right to present a defense.
The Supreme Court disagreed. It held that the per se exclusion of polygraph evidence in court-martial proceedings does not unconstitutionally abridge an accused service member’s right to present a defense. The Court reasoned that there is no consensus that polygraph evidence is reliable, that the government has legitimate interests in ensuring reliable evidence and in preserving the jury’s role in assessing credibility, and that a categorical rule serves those interests without violating the Constitution. After Scheffer, an accused cannot successfully argue that the right to present a defense requires admission of a favorable polygraph result.
The limitation applies even to a favorable result for the defense
A common misunderstanding is that the exclusion protects only the government. In fact, the rule cuts both ways, and Scheffer itself involved a defense effort to admit a favorable result. A service member who passes a polygraph cannot use that outcome at trial to bolster a claim of innocence. This often surprises members who agreed to testing precisely because they expected a clean result to help them. The favorable chart has no evidentiary value at the court-martial.
Why investigators still use polygraphs
Despite being inadmissible at trial, polygraphs remain common investigative tools. Investigators may use an examination to develop leads, to assess where to focus, or, most significantly, to elicit admissions. Statements a member makes before, during, or after an examination can be a separate matter from the polygraph result itself. While the polygraph charts and the examiner’s opinion are barred, a voluntary confession or incriminating statement made in connection with the process may be admissible on its own terms, subject to the usual rules on voluntariness and Article 31 warnings. This is why agreeing to a polygraph during an investigation carries real risk even though the result cannot be shown to the panel.
Narrow contexts and careful exceptions
The exclusion at trial on the merits is the dominant rule, but counsel should be attentive to limited situations that are analytically distinct. The bar applies to the use of the examination as evidence of guilt or innocence before the factfinder. Collateral administrative or screening uses of polygraphs, such as in certain security clearance or counterintelligence contexts, operate outside the courtroom and are governed by different policies, not by the trial rule of evidence. Those uses do not make polygraph results admissible at a court-martial. Counsel must also guard against indirect references that could effectively place the existence of an examination before the members, since the rule reaches references as well as results.
Practical guidance for service members
The most important practical point is that a polygraph cannot help you at trial, but it can hurt you. Because a favorable result is inadmissible, taking an examination offers no courtroom benefit to a member who hopes to prove innocence. At the same time, the examination process is designed to encourage statements, and any admissions made can have independent legal consequences. Before agreeing to any examination during an investigation, a service member should consult defense counsel and consider exercising the right to remain silent and the right to counsel under Article 31. Understanding that the polygraph itself is a one-way risk, with no upside in the courtroom, is essential to making an informed decision.
Conclusion
The central limitation is straightforward and powerful. Military Rule of Evidence 707 categorically excludes polygraph results, examiner opinions, and references to taking or refusing an examination from a court-martial, and the Supreme Court in United States v. Scheffer upheld that exclusion against a constitutional challenge. The rule applies to both sides, so even a favorable result is inadmissible. Service members should recognize that while the test cannot help their defense at trial, statements made during the process can be used against them, making early legal advice critical.
Disclaimer
This article is provided strictly for general educational and informational purposes. It is intended to explain how the Uniform Code of Military Justice (UCMJ), the Rules for Courts-Martial, the Military Rules of Evidence, and related military administrative processes work as a matter of public legal education. It does not constitute legal advice, a legal opinion, or a recommendation about any particular case, and it is not a substitute for advice from a qualified military defense attorney who can evaluate the specific facts and command, service, and jurisdictional circumstances involved.
Reading this article, or contacting any website on which it appears, does not create an attorney-client relationship between the reader and any law firm, attorney, or author. Every court-martial, nonjudicial punishment action, administrative separation, and security-clearance matter turns on its own facts, the charged articles, the convening authority, the service branch, and the evidence, and outcomes vary widely from one case to another.
Military law also changes over time. The Military Justice Act of 2016 (effective January 1, 2019) and subsequent National Defense Authorization Acts renumbered and rewrote many punitive articles, revised the Article 32 preliminary hearing, and altered sentencing, clemency, and appellate procedures. Statutes, regulations, executive orders, the Manual for Courts-Martial, and decisions of the service Courts of Criminal Appeals and the Court of Appeals for the Armed Forces may have been amended, superseded, or reinterpreted after this article was written, and article numbers or procedures cited here may have changed.
For these reasons, no reader should act or decline to act based on this content without first consulting a licensed attorney experienced in military justice about their own situation. The author and publisher make no warranty, express or implied, as to the accuracy, completeness, timeliness, or current applicability of the information provided, and disclaim any liability for any action taken or not taken in reliance on it. If you are facing investigation, charges, or an adverse administrative action, time limits may apply, and you should seek qualified counsel promptly.