Rule 603 – Oath or Affirmation to Testify Truthfully

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.

Summary and Explanation

Federal Rule of Evidence 603 deals with the requirement for witnesses to take an oath or affirmation before testifying in court. Here’s a summary and explanation of the rule:

  1. Oath or Affirmation Requirement: The rule requires that every witness must take an oath or affirmation before testifying. This is a formal declaration that their testimony will be truthful.
  2. Purpose of the Oath or Affirmation: The oath or affirmation is intended to impress upon the witness the duty to speak truthfully. It serves as a moral or religious reminder of the importance of honesty and the potential consequences of lying under oath.
  3. Form of the Oath or Affirmation: The exact form of the oath or affirmation is not specified in the rule, allowing for flexibility to accommodate different religious beliefs and cultural practices. The key element is that the witness must acknowledge an obligation to testify truthfully in a manner that is meaningful to them.
  4. Legal Implications: Testifying under oath or affirmation has legal implications. If a witness is found to have lied under oath, they can be charged with perjury, a serious criminal offense.

By requiring an oath or affirmation, Rule 603 aims to enhance the reliability of testimony and uphold the integrity of the judicial process. It reflects the legal system’s reliance on witness honesty and the serious implications of providing false testimony in a court of law.


(Pub. L. 93–595, §1, Jan. 2, 1975, 88 Stat. 1934; Mar. 2, 1987, eff. Oct. 1, 1987; Apr. 26, 2011, eff. Dec. 1, 2011.)

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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