Mich. Comp. Laws § 722.23

Sec. 3. As used in this act, "best interests of the child" means the sum total of the following factors to be considered, evaluated, and determined by the court: (a) The love, affection, and other emotional ties existing between the parties involved and the child. (b) The capacity and disposition of the parties involved to give the child love, affection, and guidance and to continue the education and raising of the child in his or her religion or creed, if any. (c) The capacity and disposition of the parties involved to provide the child with food, clothing, medical care or other remedial care recognized and permitted under the laws of this state in place of medical care, and other material needs. (d) The length of time the child has lived in a stable, satisfactory environment, and the desirability of maintaining continuity. (e) The permanence, as a family unit, of the existing or proposed custodial home or homes. (f) The moral fitness of the parties involved. (g) The mental and physical health of the parties involved. (h) The home, school, and community record of the child. (i) The reasonable preference of the child, if the court considers the child to be of sufficient age to express preference. (j) The willingness and ability of each of the parties to facilitate and encourage a close and continuing parent-child relationship between the child and the other parent or the child and the parents. A court may not consider negatively for the purposes of this factor any reasonable action taken by a parent to protect a child or that parent from sexual assault or domestic violence by the child's other parent. (k) Domestic violence, regardless of whether the violence was directed against or witnessed by the child. (l) Any other factor considered by the court to be relevant to a particular child custody dispute.