How accurate is paternity testing

Here is the situation: A man has a paternity test done. He knows the woman had "relations" with several close family members but she claims he is the father. Paternity test came back 98% BUT said the paternal allele did NOT match and this could be due to a close family member actually being the father.

If the paternal allele does NOT match, assuming there are no errors or genetic mutations, doesn’t that mean he is NOT the father and it is most likely one of the other family member’s child?

Is there a test that could be more certain? Child support depends on this so we want to be CERTAIN.


Great question.

Paternity testing involves comparing specific regions of DNA, regions which vary from individual to individual, but regions which are also inherited from one’s parents.

If several of the genetic regions tested do not match, then it is possible to EXCLUDE someone as being the genetic father of a child. You might want to contact the company that performed the test and ask them specifically if he was EXCLUDED from being the genetic father.

If, however, some of the regions match, then statistical testing is done to calculate the odds that two random people would share those same genetic markers.

At this point, the problem now involves an element of probability (see Paternity Testing). What are the odds that two random people will have those same markers in common? Unfortunately, it is POSSIBLE that two unrelated people will have the exact same markers—just due to a chance occurrence. But, this type of chance occurrence is extremely rare. It is like the odds of flipping a coin and having it turn out to be heads a thousand times in a row—it is very unlikely to happen, but it COULD happen.

Because paternity testing involves an element of probability, it is not possible to conclude with 100% certainty that someone is the genetic father of a child (see paternity testing). Just as it is not possible to say that someone will not flip heads a thousand times in a row. It is possible for nonrelated individuals to share very similar markers (again this is extremely unlikely, but possible).

Accordingly, to prove paternity the bar is not set at 100%, because it is not possible to achieve that degree of certainty. You can never completely rule out the possibility that a non-related individual might share the same genetic markers. As such, the standard for paternity is never 100%, but it is set as high as possible (usually at least at 99%) in order to achieve a high degree of certainty.

So, where does this leave you? Clearly there are some shared genetic markers, enough to establish some degree of relatedness, but perhaps not enough to prove paternity. And given the circumstances involved, it might be wise to test the other potential fathers before reaching any conclusions.

And we strongly encourage you to talk to an attorney who specializes in paternity testing. At this point, the problem you are trying to resolve is not likely to be answered through more testing, but more as a legal issue: How are the results of a paternity test interpreted in the state in which you reside?

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