How accurate are paternity DNA tests?

This is a common question we are always asked. So, how accurate are paternity DNA tests?

It is important to know what our scientists are looking for when we test your DNA samples. First we sequence the DNA samples. This provides us with a list of 24 DNA locations, with a pair of numbers at each location. Next, we compare each pair of numbers between the biological mother and child. After this, we end up with one column of numbers for the child. This is then compared to the potential father’s pair of numbers.

So from this analysis, the following results are then possible:

Probability of Paternity: Test involving the mother’s DNA sample

Inclusion: Based on evidence of DNA analysis, there is a greater than 99.999% probability. The results are consistent with paternity in this case.

Exclusion: Based on evidence of DNA analysis, the father is excluded for paternity. In other words, the probability of paternity is 0%. The results are inconsistent with paternity in this case.

Also, this applies to paternity tests performed without the mother’s sample. But, you may see a slight drop in the percentage of probability. For example, this may reduce to 99.9%. But this is still proof of paternity. Please note, ‘motherless paternity’ tests are not allowed for legal purposes. Only in exceptional cases will a court accept DNA results when the mother is not available.


Why is the probability of paternity not 100%?

This is a statistical quirk! We cannot say 100% because we would have to test every other human male on the planet!

So we can assure you that where there is a probability of paternity of 99.99%, this is still proven.


What if potential fathers are related?

If this is the case then you need to let us know. As such, we will need to test both potential fathers to provide a full result. They could be brothers, cousins or other family relative.

If only one related father is available, only an exclusion DNA result will be valid. This is because the related fathers’ DNA will be closely matched. As a result, it will not be possible to provide a valid inclusion result in this case.

Finally, if you have any questions about the above information, please call us on 0800 988 7107. Our team of advisors are at hand to assist. In addition, there is helpful information about the paternity DNA test on the DNA Clinics Boots webpage. Or, you can email us at [email protected]