IC 5-8-1-9: Oaths

Sec. 9. At the time and place appointed, and before the senate proceeds to act on the impeachment, the secretary must administer to the president of the senate, and the president of the senate to each of the members of the senate then present, an oath, truly and impartially to hear, try and determine the impeachment; and no member of the senate can vote or act upon the impeachment, or upon any question arising thereon, without having taken such oath.