Understanding Paternity Test Results-Explanation and Example of Legal & Non-Legal, Positive & Negative
Paternity results are used to determine the biological relationship between a man and a child, establishing whether the man is the biological father of the child in question. These results are typically obtained through a paternity test, which is a genetic analysis of the DNA of the alleged father, the child, and, if available, the mother. The test compares specific DNA markers called genetic loci to assess the likelihood of paternity.
Here’s how paternity results are usually explained:
- DNA Matching: The test compares genetic markers of the child with those of the alleged father. The biological father and child will typically match with at least 1 allele in each genetic marker, unless there is a genetic mutation.
- Probability of Paternity: The results are presented as a probability or percentage, indicating the likelihood that the alleged father is the biological father of the child. A probability of 99% or higher is considered as a positive confirmation of paternity. While a probability of 0% indicates that the tested man is not the biological father.
- Inclusion vs. Exclusion: Inclusion means that the alleged father cannot be excluded as the biological father because the genetic markers match sufficiently. Exclusion, on the other hand, means that the genetic markers do not match enough to consider the man as the biological father.
- Legal vs Non-Legal Tests: Paternity tests can be conducted for legal or non-legal purposes. Legal tests follow specific procedures to be admissible in court, and the chain of custody is strictly maintained. Non-legal tests may provide the same results but might not be admissible in court.
- Chain of Custody: For legal paternity tests it is essential to ensure the integrity of the test results by maintaining a proper chain of custody during sample collection and testing. This means samples must be collected and handled in a way that ensures they are not tampered with or contaminated.
- Accuracy: Paternity tests are highly accurate when conducted by reputable laboratories. However, the accuracy can still vary depending on the quality of the samples and the testing methods used.
Below are two examples of paternity test results. The first set represents a legal paternity test, displaying a negative result. It’s essential to acknowledge that legal tests come with a documented chain of custody. The second set represents a non-legal paternity test, demonstrating a positive result.
Negative Paternity Result Explained
In the below illustration, we have a genetic analysis involving Jane Doe as the child and John Doe as the alleged father. The DNA analysis is presented with three distinct lines for each genetic marker. The initial line represents the specific genetic marker under examination. The subsequent line denotes “C,” indicating the child’s genetic data, while the final line signifies “AF,” representing the genetic data of the alleged father.
Genetic markers in individuals manifest as alleles, which are represented as numerical values in the report. Each person possesses either one or two alleles in their genetic markers. In the case of two alleles, one is inherited from the mother, and the other from the father. Conversely, when a single allele is present, it indicates that it was inherited from both the mother and the father.
The initial marker listed in the report is D3S1358. The child’s genetic profile reveals a single allele with a value of 14, while the alleged father’s profile presents two alleles, with values 14 and 17. Notably, there is a match of the allele 14 in this particular marker. Nevertheless, upon examining the fourth marker, FGA, it becomes evident that they do not exhibit a matching pattern.
When the child and the alleged father show discrepancies in one or two genetic markers, these variations may be attributed to genetic mutations. However, if there are three or more markers where mismatches occur, it leads to the exclusion of the alleged father as a possible biological parent. In the case of John and Jane’s report, a total of 8 exclusions have been identified and listed explicitly in the conclusion. As a result of these exclusions, there is a 0% probability of John being the biological father.
Positive Paternity Result Explained
Presented below is a report obtained from a home testing kit. It is essential to recognize that results from home testing kits are not admissible as evidence in legal proceedings. This is due to the challenge of establishing the identity of individuals who were collected in the privacy of their own home. For instance, the alleged father could potentially substitute a sample from his best friend instead of providing his own. Notably, in the opening paragraph of the conclusion, it is stated that the laboratory is unable to ascertain the specific individual from whom the samples were collected.
This case involves the genetic testing of Jane Smith as the mother, Johnny Smith as the child, and John Smith as the alleged father. Similar to the first report, the specific genetic markers are presented in the top row, followed by “M” denoting the mother’s DNA in the row below, “C” for the child, and “AF” for the alleged father. Furthermore, the report includes a dedicated line for the Paternity Index (PI), also known as the Probability Index, representing a crucial indicator of likelihood.
The Paternity Index (PI) is individually computed for each genetic marker. As evident from the report, the PI values differ across markers. The variation in PI arises due to the frequency of a particular allele within the population. It is essential to understand that not all matches carry the same significance. The calculations take into account how frequently a specific allele occurs in a given marker within the broader population.
For instance, if the alleged father and child share a match on allele 12 in the CSF1PO marker, but allele 12 is prevalent in the population, the resulting PI will not be substantially high. On the other hand, if a match on allele 18 is rare in the D2S1338 marker, the PI will be higher, reflecting the increased statistical weight of such a match in establishing paternity. Therefore, the Paternity Index values are sensitive to the rarity or commonality of specific alleles, shaping the overall outcome and the strength of paternity determination.
In the initial marker, D3S1358, the mother’s genetic profile exhibits alleles 15 and 18, while the child’s profile shows alleles 15 and 17. As the mother is the confirmed parent, we can attribute the shared allele 15 to her. Consequently, the allele 17 must have been inherited from the paternal side. Notably, the alleged father’s genetic profile contains alleles 17 and 18, aligning perfectly with the presence of the allele 17 in the child’s profile, establishing a match.
Examining the third marker VWA, we observe that the child possesses a single allele with a value of 17. As mentioned earlier, this implies that the child inherited the allele 17 from both their mother and father. In this scenario, the mother’s genetic profile displays alleles 14 and 17, while the father’s profile exhibits alleles 17 and 19. Consequently, both the alleged father and the mother share a match with the child at this marker.
The final marker, DYS392, is a Y-chromosome marker. Y-chromosomes are exclusively inherited through the male lineage, and females do not possess Y-chromosomes. Consequently, at this marker, the mother would not exhibit any information, and for a biological father and a male child, matching is expected to occur.
In every genetic marker subjected to testing, the genetic profiles of the alleged father and the mother were found to be a match with that of the child. Consequently, the conclusion indicates that the father cannot be excluded as a potential biological parent. This leads to a high level of certainty, with a 99.99% probability, that he is indeed the biological father.
Test Me DNA is dedicated to providing the support you need to better understand your paternity results. Our specialized team of experts is here to guide you through the intricacies of DNA testing, ensuring clarity and accuracy in the interpretation of your results. We understand that paternity testing can be an emotional process and results may seem complex. Our professionals are equipped with the knowledge and experience to address any questions or concerns you may have. With our commitment to confidentiality and customer service, you can trust Test Me DNA to help you navigate through this important journey of discovering your biological relationships with confidence and peace of mind.