Consider the early days of courtroom drama: where a resistant father would be wrestled into court and a jury would compare the physical features of the alleged father and the fatherless child in question to render their verdict. In later years, blood grouping tests were performed, but this only served to rule out a certain class of blood types (such as men with type A, B, or O blood types). Cases were often dismissed if witnesses could show that the mother had sexual relations with other men during the same time as the alleged father.
Today, the use of DNA testing for positive identification in paternity litigation has rendered most of the previous legal practice and procedure obsolete. The alleged father need only submit a painless DNA sample (usually in the form of a saliva swab) to prove or disprove his parentage. DNA matching has replaced the Human Leukocyte Antigen (HLA) Test, which was used to match not only blood type, but also tissue type and other genetic factoring. Experts had asserted that the HLA was at least 98 percent accurate. But presumptive fathers (based upon HLA results) could rebut those presumptions by proving they were out of the state, impotent (in pre-Viagra years), or sterile at the time the child was conceived. Conversely, DNA testing has a more conclusive accuracy (close to 100 percent) that becomes almost impossible to defeat.