A paternity case is a case that decides who the father of a child is. Using the courts to decide who the father of your child is called “establishing paternity.” The biological parents of a child only file this kind of case when they were never married to each other. If the biological parents of a child are married to each other, they do not need to file a paternity case. The law assumes that the mother's husband is the father of the child.
In a paternity case, the court can order genetic marker tests (gene tests) to decide who the father is. A judge will order these tests if the man denies that he is the father, or if there is a question about who the father is. If the judge orders testing, then the mother, father, and child all have to get tested. But they do not have to get tested at the same time. The test is just a swab of the inside of your cheek. No one has to give any blood.
The judge’s decision about who is the father is a “judgment.” Getting this kind of judgment is called "establishing paternity." The court can then order child support, custody, visitation, medical insurance, and other things that are in the best interests of your child.