Credibility is the heart of most contested military proceedings, and not all of the signals a factfinder uses are spoken. A witness who hesitates, contradicts an earlier statement through a gesture, refuses to answer, or behaves in a way that suggests evasion may give the opposing party material to challenge believability. The question is whether, and how, that nonverbal conduct can be brought to bear under the Military Rules of Evidence during a hearing. The short answer is that demeanor and conduct can influence credibility, but the rules carefully channel how a party may use them, and several categories of nonverbal behavior raise distinct issues.
Demeanor as a permissible basis for assessing credibility
Military factfinders are expected to weigh the demeanor of witnesses. The manner in which a witness testifies, including tone, hesitation, body language, and apparent candor or evasiveness, is a traditional and accepted part of judging credibility. A panel or a military judge sitting alone may consider how a witness behaved on the stand when deciding how much weight to give the testimony. This is one reason appellate courts defer to the factfinder on credibility: the reviewing court did not see the witness. So in the most basic sense, nonverbal conduct observed during live testimony is already part of the credibility calculus, and counsel may argue from it in closing.
Cross-examination and the scope rule
Counsel can also draw out and expose nonverbal conduct through questioning. Under Military Rule of Evidence 611(b), cross-examination may reach matters affecting the credibility of the witness. A cross-examiner can ask a witness to explain a gesture, a pause, or a refusal, and can press a witness whose conduct on the stand appears inconsistent with the words being spoken. When a witness shakes the head while saying yes, or points to something while denying knowledge of it, counsel may legitimately develop that on the record so the factfinder appreciates the inconsistency.
Conduct as a prior inconsistent statement
Some nonverbal conduct qualifies as a statement. The Military Rules of Evidence treat assertive conduct, conduct intended as a substitute for words, as a statement. If a witness previously gestured an answer, nodded affirmatively, or pointed to identify a person, that assertive conduct can be a prior statement. Where it is inconsistent with the witness’s in-court testimony, it may be used to impeach under Military Rule of Evidence 613, which governs prior inconsistent statements. The conduct must have been intended as an assertion to be treated this way; purely reflexive or involuntary movement is not a statement.
Specific instances of conduct under Rule 608
Military Rule of Evidence 608 permits a party to attack a witness’s character for truthfulness. On cross-examination, counsel may inquire into specific instances of the witness’s conduct if those instances are probative of truthfulness or untruthfulness, but the rule generally bars proving those instances by extrinsic evidence. This matters for nonverbal conduct that occurred outside the hearing. A party may ask a witness about prior deceptive acts that bear on honesty, but if the witness denies them, the questioner ordinarily must accept the answer and cannot bring in outside proof solely to contradict it on a collateral point.
Bias, motive, and conduct that reveals them
Nonverbal conduct can also reveal bias or motive to misrepresent. Unlike specific instances offered to show general untruthfulness, bias may be shown by extrinsic evidence. If a witness’s gestures, reactions toward a party, or conduct in the courtroom suggest hostility, fear, or a stake in the outcome, counsel may develop that both through the witness and, where appropriate, through other evidence, because impeachment for bias is not confined to the witness’s own answers.
Refusal to answer and invocation of rights
Some nonverbal conduct is a refusal to cooperate. A witness who declines to answer, or who properly invokes a privilege, presents a different problem. A factfinder generally may not draw an adverse credibility inference from a witness’s lawful exercise of a privilege against self-incrimination, and the rules and case law restrict comment on a proper invocation. By contrast, an unjustified refusal to answer a proper question, after being directed to respond, can affect the weight the factfinder gives the rest of the testimony. Counsel must be careful to distinguish protected silence from simple evasiveness.
Limits the judge will enforce
A military judge polices these uses under Military Rule of Evidence 403, which allows exclusion when the probative value of evidence is substantially outweighed by unfair prejudice, confusion, or waste of time. Inviting a panel to speculate about ambiguous body language, or to treat nervousness as proof of lying, can be more prejudicial than probative. The judge may also limit questioning that ventures into collateral matters, and may give instructions clarifying that the factfinder, not counsel, decides what a witness’s demeanor means. A lay witness generally may describe what another person did, but may not offer an opinion that the person was lying, since that intrudes on the factfinder’s province.
Putting it together
So nonverbal conduct can be used to challenge credibility during a hearing, but through defined channels. Live demeanor is already available to the factfinder and may be argued. Counsel may expose and explore conduct through cross-examination under Rule 611, impeach with assertive conduct that amounts to a prior inconsistent statement under Rule 613, inquire into truth-related specific instances within the limits of Rule 608, and prove bias revealed by conduct, sometimes with extrinsic evidence. Throughout, the military judge applies Rule 403 and the rules against improper opinion and improper comment on protected silence. Because the line between fair impeachment and improper speculation is fact dependent, parties seeking to use a witness’s conduct to attack credibility should be prepared to tie the conduct to a specific evidentiary basis recognized by the rules.
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.
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