The claim by any witness that any testimony sought to be elicited may tend to incriminate him or her shall not excuse such witness from testifying, but such evidence or testimony shall not be used against such person on the trial of any criminal proceeding, excepting in a prosecution for perjury. The commissioner shall have power to compel the attendance of witnesses at any place within the state.

Powers of each commissioner to compel attendance of witnesses: RCW 80.04.020.