The presiding judge may not testify as a witness at the trial. A party need not object to preserve the issue.
Notes of Advisory Committee on Proposed Rules
In view of the mandate of 28 U.S.C. §455 that a judge disqualify himself in “any case in which he * * * is or has been a material witness,” the likelihood that the presiding judge in a federal court might be called to testify in the trial over which he is presiding is slight. Nevertheless the possibility is not totally eliminated.
The solution here presented is a broad rule of incompetency, rather than such alternatives as incompetency only as to material matters, leaving the matter to the discretion of the judge, or recognizing no incompetency. The choice is the result of inability to evolve satisfactory answers to questions which arise when the judge abandons the bench for the witness stand. Who rules on objections? Who compels him to answer? Can he rule impartially on the weight and admissibility of his own testimony? Can he be impeached or cross-examined effectively? Can he, in a jury trial, avoid conferring his seal of approval on one side in the eyes of the jury? Can he, in a bench trial, avoid an involvement destructive of impartiality? The rule of general incompetency has substantial support. See Report of the Special Committee on the Propriety of Judges Appearing as Witnesses, 36 A.B.A.J. 630 (1950); cases collected in Annot. 157 A.L.R. 311; McCormick §68, p. 147; Uniform Rule 42; California Evidence Code §703; Kansas Code of Civil Procedure §60–442; New Jersey Evidence Rule 42. Cf. 6 Wigmore §1909, which advocates leaving the matter to the discretion of the judge, and statutes to that effect collected in Annot. 157 A.L.R. 311.
The rule provides an “automatic” objection. To require an actual objection would confront the opponent with a choice between not objecting, with the result of allowing the testimony, and objecting, with the probable result of excluding the testimony but at the price of continuing the trial before a judge likely to feel that his integrity had been attacked by the objector.
Committee Notes on Rules—2011 Amendment
The language of Rule 605 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.