Mich. Comp. Laws § 6.4
Whenever an impeachment is directed the senate shall forthwith, after the hour of final adjournment of the legislature, be organized into a court for the trial of the same at the state capital, and such organization shall be deemed to be perfected when the presiding officer of the senate and all the members thereof, present, shall have taken oath or affirmation hereinbefore prescribed, and no member of the court shall sit, or give his vote upon such trial, until he shall have taken such oath or affirmation, which oath or affirmation shall be administered by the secretary of the senate, to the presiding officer thereof, and by the presiding officer to each of the members of the senate. The senate sitting upon the trial of an impeachment shall have the same power to compel the attendance of its members, as when engaged in the ordinary business of legislation.
MCL 6.4