A paternity test establishes a biological relationship between a child and an alleged father. It analyzes genetic material to determine if a shared inheritance pattern exists. The test provides clarity regarding biological parentage, which can be significant for legal, medical, or personal reasons. Understanding how to interpret these results helps you comprehend the scientific findings in your report.
Understanding the Science Behind the Test
Paternity testing relies on DNA, the unique genetic blueprint found in every individual. DNA, inherited from both biological parents, acts as the instruction manual for life. Specific regions of DNA, known as genetic markers or loci, vary significantly between individuals, making them useful for identification.
During a paternity test, scientists analyze these specific genetic markers from samples provided by the child, the alleged father, and typically the mother. Each person inherits one copy of each genetic marker from their biological mother and one from their biological father.
Comparing the child’s genetic markers to the alleged father’s determines if a paternal link exists. Matching alleles—different forms of a gene at a specific locus—between the child and alleged father across many DNA points provide the basis for concluding paternity.
Deciphering the Report’s Key Data
A paternity test report typically presents a detailed breakdown of the genetic markers analyzed. Reports often list “Loci,” specific DNA locations where genetic variation is examined. For each locus, the report displays the “Alleles” identified for the child, the mother, and the alleged father. These alleles are represented by numbers that indicate the size or specific sequence of the DNA fragment at that particular locus. For a biological father, one of the child’s alleles at each locus must match one of the alleged father’s alleles, assuming the other allele comes from the mother.
The report also commonly includes an “Individual Paternity Index” (PI) for each locus. The PI is a ratio that quantifies the likelihood that the alleged father transmitted the observed paternal allele to the child, compared to a random, unrelated man in the population. A high PI value for a locus indicates strong support for paternity at that specific genetic marker, while a PI of zero suggests non-paternity for that locus.
Interpreting the Probability of Paternity
The individual Paternity Index (PI) values from each analyzed locus are combined mathematically to generate a “Combined Paternity Index” (CPI). The CPI represents the overall likelihood of the alleged father being the biological parent compared to an unrelated man. This index is calculated by multiplying all the individual PIs together across all the loci examined in the test. A higher CPI value indicates a much stronger statistical likelihood of paternity.
The CPI is then converted into the “Probability of Paternity” (POP), which is expressed as a percentage. This percentage represents the probability that the alleged father is the biological parent, given the genetic results. For instance, a high POP, typically 99.9% or greater, signifies that the genetic evidence supports the alleged father as the biological parent. This level of probability is generally considered conclusive for inclusion.
Conversely, a low POP, often 0%, indicates that the genetic markers do not match, meaning the alleged father is excluded as the biological parent. When genetic markers are inconsistent, the CPI will be zero, leading to a 0% Probability of Paternity. The POP provides the final statistical measure of the genetic relationship.
Reaching the Final Conclusion
The Probability of Paternity directly leads to the definitive conclusion stated on the report. If the Probability of Paternity is 99.9% or higher, the report will typically conclude that the alleged father “cannot be excluded as the biological father.” This signifies that the genetic evidence is consistent with paternity and supports the alleged father being the biological parent. It means that his DNA profile matches the child’s DNA profile in a manner consistent with biological inheritance.
If the Probability of Paternity is 0%, the report will state that the alleged father is “excluded as the biological father.” This conclusion means that there are no shared genetic markers between the child and the alleged father that would indicate a biological relationship. A 0% probability is a definitive finding of non-paternity based on scientific comparison.