What does probability of paternity 99.99 mean

The precise language used in your paternity report is very important but, because it’s also very technical, it can sometimes be hard to understand. The report language is familiar to scientists, lawyers, and judges. To help with understanding your results, we’ve also shown you how they might say it on TV, instead of in a courtroom.

Your Report

IMPORTANT: 

If you did an at-home peace-of-mind test, your report will not show the names of participants: participants are only identified by number and by their role in the test (for example, alleged father or child).

We include names of participants  on the report only for witnessed, chain-of-custody tests. 

Each paternity test report shows the following information:

• Conclusion
• Combined Paternity Index (CPI)
• Probability of Paternity
• Data table of DNA markers (or genetic systems)

The Conclusion states whether the possible father is EXCLUDED or is NOT EXCLUDED as the biological father (see explanations below). The data table lists the different DNA markers (or “genetic systems”) examined by scientists to create the CPI and Probability of Paternity.

Your Result

If the Conclusion reads, “is EXCLUDED as the biological father,” this means that he is NOT the father because the data in the table do not support a paternity relationship. When a possible father is EXCLUDED as the biological father, the Combined Paternity Index (CPI) is 0 and the Probability of Paternity is 0%.

If the Conclusion reads, “is NOT EXCLUDED as the biological father,” this means that he is most likely to BE the father because the data in the table strongly support a paternity relationship. When a possible father is NOT EXCLUDED, the Combined Paternity Index (CPI) is 100 (or larger) and the Probability of Paternity is typically 99.99% (or higher).

Why do TV personalities say “you are the father” while scientists say you are “not excluded as the biological father”?

Scientists use precise language, whereas TV personalities generalize for dramatic effect. DNA paternity testing uses powerful statistics to create a probability of paternity, and the highest probability possible is 99.99% (not 100%). Saying, “You ARE the father,” implies a 100% probability of paternity, which is technically incorrect.

So, just how powerful is a 99.99% probability of paternity?

A 99.99% probability of paternity is so powerful, that it’s routinely accepted as evidence in favor of paternity by genetic scientists, courtroom judges, and even the U.S. State Department. Although the scientific language is more technical than how they say it on TV, the bottom line is the same: a DNA paternity test probability of 99.99% is strong enough for a judge to confidently allow (or deny) child support, immigration, or even conviction in a criminal case. It’s also why a TV host feels confident enough to say, “You ARE the father.”

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