WHEN A MARRIED couple reach the decision to divorce, the challenges of the process have only begun. For couples who have children, often the most important and wrenching challenge is deciding child custody. Many parents are able to reach a mutual agreement about custody outside of the courts, but in some cases the parents cannot agree and it is up to a judge to make the final declaration. Either way, the decision is a complicated one, requiring a great deal of thought. Over the years, families, lawyers, and lawmakers have struggled to find a way to resolve child custody questions as fairly as possible for everyone involved, but this has not been an easy task.

Legal custody—little controversy

When people use the word custody, they are most often referring to physical custody—the...