Good question. A judge will have to rely upon a statute, NJSA 9:2-4, which sets forth 14 factors to be considered. Specifically, Pursuant to N.J.S.A. 9:2-4, the factors to be considered by a custody expert when making a recommendation to the Court are: 1) The parents' ability to agree, communicate and cooperate in matters relating to the child; 2) The parents' willingness to accept custody and any history of unwillingness to allow parenting time not based on substantiated abuse; 3) The interaction and relationship of the child with its parents and siblings; 4) The history of domestic violence, if any; 5) The safety of the child and the safety of either parent from physical abuse by the other parent; 6) The preference of the child when of sufficient age and capacity to reason so as to form an intelligent decision; 7) The needs of the child; 8) The stability of the home environment offered; 9) The quality and continuity of the child's education; 10) The fitness of the parents; 11) The geographical proximity of the parents' homes; 12) The extent and quality of the time spent with the child prior to or subsequent to the separation; 13) The parents' employment responsibilities; and 14) The age and number of the children.
I would explore what you mean by 'sole custody" and determine whether that is by way of a court order.