Almost all courts use a standard that gives the "best interests of the child" the highest priority when deciding custody issues. What the best interests of a child are in a given situation depends on many factors, including:
- the child’s age, sex, and mental and physical health
- the parent’s mental and physical health
- the parent’s lifestyle and other social factors, including whether the child is exposed to second-hand smoke and whether there is any history of child abuse
- the emotional bond between parent and child, as well as the parent’s ability to give the child guidance
- the parent’s ability to provide the child with food, shelter, clothing, and medical care
- the child’s established living pattern (school, home, community, religious institution)
- the quality of the child’s education in the current situation
- the impact on the child of changing the status quo, and
- the child’s preference, if the child is above a certain age (usually about 12).
Assuming that none of these factors clearly favors one parent over the other, most courts tend to focus on which parent is likely to provide the children a stable environment, and which parent will better foster the child’s relationship with the other parent. With younger children, this may mean awarding custody to the parent who has been the child’s primary caregiver. With older children, this may mean giving custody to the parent who is best able to foster continuity in education, neighborhood life, religious institutions, and peer relationships.