The county auditor, prosecuting attorney, and chair of the county legislative authority, or designees as per chapter 29A.60 RCW, shall be responsible for the performance of all duties of the county canvassing board, as set forth in chapters 29A.40 and 29A.60 RCW, and the rules on canvassing adopted by the secretary of state. These duties shall be performed by the members of the board, or they may delegate in writing representatives to perform these duties. This written delegation of authority shall be filed with the county auditor prior to any person undertaking any action on behalf of the board. In no instance may the members of the county canvassing board delegate the responsibility of certifying the returns of any primary or election, of determining the validity of any challenged ballots, or of rejecting ballots. When considering the validity or rejection of ballots, the canvassing board may review the ballots individually, in batches, or as part of a report of ballots presented to the board. In the event the canvassing board concludes that criminal activity may have occurred, the county auditor must refer the ballot and any relevant material to the county sheriff or county prosecuting attorney.