Rule 603
Oath or Affirmation to Testify Truthfully
WITNESSES
Rule Text
Before testifying, a witness must give an oath or affirmation to testify truthfully. It must be in a form designed to impress that duty on the witness’s conscience.
Plain-English Summary (for reference only — not a substitute for the rule text above)
Every witness who takes the stand in a federal court must make a formal promise to tell the truth before they start speaking. This happens before any questions are asked.
The promise can be a traditional religious oath or a non-religious affirmation. What matters is that the witness understands they are making a serious commitment to be honest. The point is to make sure the weight of that promise registers with the witness personally.
If a witness lies after taking this oath or affirmation, they can face serious legal consequences, including perjury charges. The promise is not just a formality.
Summary generated March 09, 2026
Committee Notes
Notes of Advisory Committee on Proposed Rules
The rule is designed to afford the flexibility required in dealing with religious adults, atheists, conscientious objectors, mental defectives, and children. Affirmation is simply a solemn undertaking to tell the truth; no special verbal formula is required. As is true generally, affirmation is recognized by federal law. “Oath” includes affirmation, 1 U.S.C. § 1; judges and clerks may administer oaths and affirmations, 28 U.S.C. §§ 459, 953; and affirmations are acceptable in lieu of oaths under Rule 43(d) of the Federal Rules of Civil Procedure. Perjury by a witness is a crime, 18 U.S.C. § 1621.
Notes of Advisory Committee on Rules—1987 Amendment
The amendments are technical. No substantive change is intended.
Committee Notes on Rules—2011 Amendment
The language of Rule 603 has been amended as part of the restyling of the Evidence Rules to make them more easily understood and to make style and terminology consistent throughout the rules. These changes are intended to be stylistic only. There is no intent to change any result in any ruling on evidence admissibility.
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Rule text may not reflect the most recent amendments. Always verify against official
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