At the time and place appointed, and before the Senate acts on the impeachment, the secretary shall administer to the President of the Senate, and the President of the Senate to each of the members of the Senate present, an oath truly and impartially to hear, try, and determine the impeachment. No member of the Senate can act or vote upon the impeachment, or upon any question arising thereon, without having taken such oath.
Ca. Gov. Code § 3031