Colo. Code. Jud. Cond. 3.3
A judge shall not testify as a character witness in a judicial, administrative, or other adjudicatory proceeding or otherwise vouch for the character of a person in a legal proceeding, except when duly summoned.
Colo. Code. Jud. Cond. 3.3
COMMENT
[1] A judge who, without being subpoenaed, testifies as a character witness abuses the prestige of judicial office to advance the interests of another. See Rule 1.3. Except in unusual circumstances where the demands of justice require, a judge should discourage a party from requiring the judge to testify as a character witness.
ETHICS OPINIONS A judge may not testify as a character witness on a voluntary basis, but he is obligated to comply with a subpoena if one is issued. Where a judge has been asked to provide such testimony, the judge should consider whether the interests of justice require his or her testimony, and if not should then consider attempting to discourage the subpoenaing party or lawyer from requiring the testimony, because of the possibility that the testimony is being sought to trade on the judge's position. Colo. J.E.A.B. Op. 06-03. A judge may not write a letter to the pardon board at the request of convicted felon sentenced by the judge, nor should the judge write such a letter of the judge's own initiative. Alaska Ad. Op. 2003-01. A judge should not testify as a character witness for a criminal defendant in a trial unless the judge has been subpoenaed. The giving of such character testimony by judges should be discouraged, and is appropriate only where a subpoena makes it unavoidable. Utah Ad. Op. 88-09.