Paternity evidence

DEFINITION: Evidence used to determine whether a person is the father of a specific child.

SIGNIFICANCE: Information on paternity can be important for a number of legal reasons, from issues of inheritance to cases involving rape. Most often, tests for paternity are conducted using DNA evidence. Forensic scientists compare the DNA of an alleged father to a child’s DNA to determine whether there is evidence of paternity based on the fact that the man cannot be excluded as the father of the child.

Before forensic experts began to analyze DNA (deoxyribonucleic acid), the used in paternity cases was far from conclusive. Courts in the United States applied a common-law “presumption of paternity” after a mother named a particular person as the father of her child. The alleged father might rebut the presumption by producing evidence such as sterility or impotence or evidence showing that he was not present in the same location as the mother at the time of conception. Because of the lack of definitive evidence, however, many cases of paternity were perpetrated, as most US states did not require mothers to disclose the names of all potential fathers of their children.

Although modern methods of examining DNA evidence may exclude a person as the fraternal parent of a child with almost 100 percent accuracy, scientists have not yet been able to use DNA to prove positively that a specific person is the father. In addition, paternity fraud still exists in those courts that are slow to accept some of the newer technologies used by forensic scientists to establish paternity. After paternity has been established, the person designated as the father may find it difficult to obtain rescission of the paternity court order, even if more sophisticated evidence is produced at a later date.

Reasons for Establishing Paternity

Establishing paternity serves several purposes. One of the largest demands for paternity testing relates to child support. The government wants to make sure that parents pay to support their children rather than have taxpayers fund child support through public assistance. In fact, US law requires a woman to name possible fathers in order to obtain public assistance for her children.

Paternity must also be established before children and fathers are able to inherit from each other under state intestacy laws that require a biological relationship. Insurance companies and the government may also require a father-child determination before paying insurance or Social Security benefits. Children may want to know the identities of their biological fathers for personal, medical, and emotional reasons. Finally, it is important to identify fathers for purposes of prosecution in criminal paternity cases such as rape, sexual abuse of a child, and incest.

Blood and DNA Heredity Evidence

In some paternity cases, forensic serologists may still use blood typing. Using blood as the only evidence to establish paternity, however, has limitations, not the least of which is the amount of blood evidence needed to run such tests and the lack of genetic information generated from blood typing.

DNA provides better evidence of paternity, as it is unique and the hereditary factors found in DNA work well to exclude people as biological parents of a child. Half of a person’s DNA is contributed by the mother and the other half by the father. By comparing the specific short tandem repeats (STRs) of a child’s DNA to the DNA of possible parents of the child, forensic scientists are able to identify people who could not be the mother and father based on dissimilarities in their DNA (assuming a genetic mutation did not result in a false exclusion). To determine the most likely father, forensic scientists use probability calculations after finding consistent genetic patterns between the DNA of the alleged father and the child.

Sources of DNA Evidence

The most credible way to test for paternity is by comparing samples of DNA extracted from body fluids (such as saliva, semen, or blood) collected directly from the purported father and the child. Noninvasive buccal samples—collected by scraping the inside of the mouth with a foam applicator or cotton swab—may also be used; this method is especially useful for collecting DNA from infants. When an individual of interest is not available, scientists must collect DNA evidence from some other source that person has left behind. For example, paternity testing can be conducted with a small DNA sample obtained from a hair (with the root intact) left in a hairbrush or from saliva on a toothbrush, envelope flap, or cigarette butt. The blood in the umbilical cord of a newborn or cells from a fetus also provide sufficient DNA for testing.

In some cases, the purported father or child is deceased, and DNA samples are collected during autopsy or from the body at the funeral home. If a case requires DNA from a body after burial, a court-ordered exhumation may take place so that a specimen can be collected. For children, DNA exemplars may be available from dried blood samples stored on so-called Guthrie cards, which many US states use to screen for genetic diseases at the time of birth. In criminal paternity cases involving fetuses aborted before full term, DNA from the fetuses can be compared with the DNA of the alleged fathers.

Bibliography

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Buckleton, John, Christopher M. Triggs, and Simon J. Walsh, eds. Forensic DNA Evidence Interpretation. Boca Raton, Fla.: CRC Press, 2005.

Butler, John M. Forensic DNA Typing: Biology, Technology, and Genetics of STR Markers. 2d ed. Burlington, Mass.: Elsevier Academic Press, 2005.

Coleman, Howard, and Eric Swenson. DNA in the Courtroom: A Trial Watcher’s Guide. Seattle: GeneLex, 1994.

Evett, Ian W., and Bruce S. Weir. Interpreting DNA Evidence: Statistical Genetics for Forensic Scientists. Sunderland, Mass: Sinauer Associates, 1998.

Kobilinsky, Lawrence F., Thomas F. Liotti, and Jamel Oeser-Sweat. DNA: Forensic and Legal Applications. Hoboken, N.J.: Wiley-Interscience, 2005.

"Population Genetics and Statistics for Forensic Analysts: Parentage and Relatedness." National Institute of Justice, 17 July 2023, nij.ojp.gov/nij-hosted-online-training-courses/population-genetics-and-statistics-forensic-analysts/statistics/parentage-and-relatedness. Accessed 16 Aug. 2024.