Compiled Laws, Chapter 750. Michigan Penal Code § 750.318

Sec. 318. The jury before whom any person indicted for murder shall be tried shall, if they find such person guilty thereof, ascertain in their verdict, whether it be murder of the first or second degree; but, if such person shall be convicted by confession, the court shall proceed by examination of witnesses to determine the degree of the crime, and shall render judgment accordingly. All testimony taken at such examination shall be taken in open court and a typewritten transcript or copy thereof, certified by the court reporter taking the same, shall be placed in the file of the case in the office of the county clerk.