A paternity test is used to ascertain who is the father of another person. It is frequently done by DNA analysis of the child and the possible father. Since a person's DNA is the same in all of their cells, DNA testing can be done with a blood sample, a swab of skin, or a lock of hair. A comparison of two people's DNA sequences will indicate the extent to which they are biologically related. Paternity tests make it easier for the courts to establish grounds to order the so-called "dead beat" fathers to pay child support.
Prior to the DNA test a paternity test would be done by getting the blood type for the child, mother and potential father. Since there are obviously many men with the same blood type it was not possible to prove that a man was the father, only that he was not.
Both DNA and blood typing tests can be used to determine the mother of the child.