Can Blood Type Determine Paternity?

This is a question that is often asked by people inquiring about performing a paternity test. Unfortunately, you cannot determine paternity by using the blood type method alone. Each person inherits ABO Blood Type from their parents. For Example, If a mother is O blood type and both of the alleged fathers are A blood type and the child has an A blood type. There is no way to determine paternity of two or alleged fathers share the same blood type.

Now, If we use the same example where the child has an A blood type and one of the alleged fathers has a B blood type. We can definitively conclude that the alleged father with type B blood is not the biological father of the child with the A Blood Type. It is important to note, that both A and B Blood Types are dominant types. Therefore one dominant cannot create the other dominant type. Blood Typing can be used to exclude a father but to determine a biological relationship between an alleged father and child.