Blood Groups and Paternity
Can blood groups prove a paternity, no and yes. Yes, it can prove A is not the father of B but it can not prove A is the father of B. Let me just quote, Britanica,
“ Although blood group studies can’t be used to prove paternity, they can prove the unequivocal evidence that a male is not father of a particular child. Since the red antigen cells are inherited as a dominant traits, a child cannot have a blood group antigen, that is not present in one or both the parents. For example, if the child in question belongs to group A and mother and putative father are group O, the man is excluded from the paternity.”
Thus, it can only be a negative test to exclude paternity and not a positive test to prove paternity. There are only four type of blood groups A, B, O and AB and even if add + and – it will be 8 and the entire population is divided into that 8 group so probability is very high and among the some blood groups are common and some rare.
Let me quote another article and author is, Jill Adams, Ph.D. (Freelance Science Writer, Albany, NY.) © 2008 Nature Education Citation: Adams, J. (2008) Paternity testing: blood types and DNA. Nature Education 1(1):146
“In cases of questioned paternity, ABO blood-typing can be used to exclude a man from being a child's father. For example, a man who has type AB blood could not father a child with type O blood, because he would pass on either the A or the B allele to all of his offspring. Despite their usefulness in this regard, ABO blood groups cannot be used to confirm whether a man is indeed a child's father. Because of this and several other factors, it took the legal system some time to trust blood-typing. For example, in a famous case in 1943, the starlet Joan Barry accused actor Charlie Chaplin of fathering her child.Blood tests definitively excluded Chaplin as the father.”.
Summary
For years, questions of paternity presented a significant challenge to scientists and potential parents alike. During the first half of the twentieth century, researchers often turned to people's ABO phenotypes when such issues arose; however, ABO blood group information could only be used to exclude potential fathers, rather than confirm the presence of a parental relationship. Consideration of additional blood markers, such as Rh antigens, MN antigens, and HLAs, greatly increased the effectiveness of paternity testing over the next few decades, but it still left significant room for error. Thus, with the dawn of DNA analysis and sequencing techniques in the 1980s and 1990s, scientists increasingly began to look at people's genomes when questions of fatherhood arose. This approach proved exceedingly useful; in fact, current marker-based methods of analysis yield test results that are both 99.99% accurate and applicable in a variety of settings. With the ongoing advancement of DNA sequencing and analytical technologies, we will no doubt continue to see an increase in the utility of these tests, as well as in the availability of detailed genetic services to the general public.”
Thus, blood group can only exclude a person to be a parent and can’t confirm that a person is father of the person with whom blood group matches.
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