Except as authorized by Iowa Code section 20.31, a mediator, arbitrator, administrative law judge, member of the board or other officer or employee of the board shall not testify on behalf of any party to a prohibited practice, representation or impasse resolution proceeding, pending in any court or before the board, with respect to any information, facts, or other matter coming to that individual's knowledge through a party or parties in an official capacity as a resolver of disputes.
Iowa Admin. Code r. 621-2.17