A DNA test is a scientific method used to establish biological relationships between individuals. It examines specific genetic markers to determine if there is a shared inheritance of DNA. When a DNA test result states “not excluded,” it indicates a very high probability that a biological relationship exists between the tested individuals.
Why “Not Excluded” is the Standard Term
DNA testing relies on an exclusionary principle, meaning it attempts to rule out individuals who do not share the necessary genetic markers. If an individual’s DNA profile contains all the markers expected for a particular relationship, they cannot be excluded as a biological relative. This approach is rooted in the statistical nature of genetic inheritance; while it’s possible to definitively exclude someone, it’s not possible to achieve 100% inclusion due to the sheer number of possible genetic variations.
Scientists compare specific regions of DNA, known as short tandem repeats (STRs), between the individuals involved in the test. For standard relationship tests like paternity, laboratories typically analyze between 16 and 24 STR markers. Each marker has different alleles, or variations, and by matching these alleles, a strong statistical likelihood of a relationship can be established.
What Your “Not Excluded” Result Means
When a paternity test result indicates “not excluded,” it signifies that the tested male is considered the biological father. This finding is accompanied by a very high Probability of Paternity, frequently reported as 99.9% or higher. Such a high probability is universally accepted as conclusive for both legal and personal purposes, effectively confirming paternity.
Similarly, for other relationship tests, such as those for siblings or grandparents, a “not excluded” result means there is a high probability of that specific biological connection. For instance, a sibling test might indicate a high probability of full or half-sibling status if the genetic profiles align.
Understanding Test Accuracy and Probability
The high accuracy of DNA relationship tests stems from the analysis of numerous distinct genetic markers and the sophisticated statistical calculations applied. One key calculation is the Combined Paternity Index (CPI), or similar indices for other relationships, which quantifies how many times more likely it is that the tested individual is the biological parent compared to a random individual from the population. This index is then converted into the Probability of Paternity, providing a clear percentage.
Factors contributing to this extremely high probability include the large number of STR markers analyzed, as more markers lead to greater certainty and a lower chance of a coincidental match. The rarity of specific alleles within populations also enhances the statistical power of the test. Reputable laboratories adhere to strict protocols for sample handling and analysis, minimizing the risk of errors such as contamination or misinterpretation, ensuring the reliability of the “not excluded” result. While genetic mutations can occur in rare instances, advanced testing methods account for these possibilities.