Tenn. Code Ann. § 40-25-124: Costs where several defendants

It is the duty of the district attorney general to include in one (1) bill of indictment or presentment all persons engaged in the same offense, and the costs shall be taxed as one (1) suit, unless the defendants sever in their trial, and, in that event, the costs are taxed as two (2) or more suits, according to the nature of the case.