Joint custody, which is also known as shared custody, has two elements: joint legal custody, which refers to equal rights and responsibilities to make major decisions for the children, and joint physical custody, which refers to the parents’ participation in the "day-to-day upbringing of the child."
More than 30 states now have statutes specifically authorizing joint custody awards, and most states now hold that the courts authority to award joint custody does not depend upon whether the parties request it.
In awarding joint custody, the single most important consideration is the ability of the parents to cooperate. In fact, in cases where both parties can cooperate for the benefit of the child, joint legal custody awards are generally upheld even when one or both parents may have sought sole custody.
Joint legal custody to both parents does not preclude sole physical custody to one parent. At the least, the parent who has physical custody must have a suitable place to live, provide adequate supervision when absent, maintain reasonable discipline, and nurture the child with affection.
In shared custody routines, courts sometimes designate one parent what is called the "primary physical custody," but allow the other parent "greater access to the child than [he or she would have] with only traditional visitation rights." At issue is the parent is "better suited to attend to the day-to-day care of the child."
Some jurisdictions permit alternating custody in a variety of routines -- weekly, by half year, with the one parent during the school year and the other during summer recess, and even annually. Some jurisdictions frown on this because it is held to be very disruptive to the child.
When it works, shared custody greatly reduces the trauma a child suffers when his or her parents part.
Not infrequently, shared custody routines break down when subsequent to their onset divorce parents demonstrate an inability to cooperate, extreme anger or hostility, serious misconduct, make false allegations about one another, or neglect the child.
All custody is subject to modification based on a showing that the change is in the best interest of the child.
Sometimes shared custodians request the court to modify the physical custody arrangements while leaving shared legal custody in place. This may happen as a result of interference by the primary physical custodian, or his or her instability, or his or her remarriage.