Probability of Paternity | DNA Testing Glossary

The probability of paternity is a statistical percentage that represents how likely it is that the tested man is the biological father of the child, based on the DNA evidence. Labs calculate it from the combined paternity index using Bayes' theorem with a prior probability (usually set at 0.5, meaning no assumption either way before testing). A probability of 99.99% or higher means the tested man is included as the biological father. A probability of 0% means he is excluded. There is no middle ground in a properly conducted test. The probability does not measure certainty about the test procedure itself — it expresses how strongly the DNA evidence supports or rules out the relationship.

Related Terms

Combined Paternity Index, Inclusion, Exclusion, Paternity Test, Alleged Father

Source

National Library of Medicine — Interpretation of DNA Identification Results