New York Consolidated Laws, Judiciary Law - JUD § 246. Oath to members of the court

At the time and place appointed, and before the court proceeds to act upon the impeachment, the clerk must administer to the presiding judge, and the presiding judge to each of the members of the court then present, an oath or affirmation truly and impartially to try and determine the impeachment;  and no member of the court can act or vote upon the impeachment, or any question arising thereon, without having taken this oath or affirmation.