For unmarried couples, paternity tests can be very important. For example, a man may say that a child is not his and he does not want to pay child support, while a woman may insist that it is his child. A lot of money is on the line, so having a test that provides definitive results is crucial.
That’s why modern paternity tests focus on DNA, not only blood types, as older tests did.
The problem with a blood test is that it doesn’t always prove who is the father; is merely helps to prove who is not the father.
There are four basic blood types, and they’re passed down. These are A, B, AB, and O. It all depends which antigens the person has, or if he or she has neither (resulting in O blood).
So, imagine that a mother has Type A blood. The alleged father has Type O blood. Their child could then have Type A or Type O, but it couldn’t have AB. If it does have AB, that would mean another man, with B or AB blood, was actually the father. The man with Type O blood could be ruled out.
The problem is obvious, though: That doesn’t mean the man is definitely the father if the child has Type O blood. Sure, it’s a match, but there are many people with Type O blood. The only way that this test offered proof was if there was not a match. If there was, it was still the man’s word against the woman’s.
DNA testing, though, is very precise. The child will be an equal split, with half the mother’s DNA and half the father’s DNA. Therefore, getting a match on a DNA test does indicate that the man is the father, and not finding a match rules him out.
Even after having a paternity test done, unmarried couples may have many questions about custody rights, child support obligations, and more, so it’s important for each parent to know his or her rights.
Source: FindLaw, “Paternity Tests: Blood Tests and DNA,” accessed July 13, 2017