A paternity test is a genetic examination that determines the biological relationship between a child and an alleged father by comparing specific regions of DNA. The test provides scientific evidence regarding fatherhood, which can be useful for various personal and legal purposes.
Sample Collection Methods
The primary method for collecting DNA samples for paternity testing involves buccal, or cheek, swabs. This non-invasive technique collects cells by gently rubbing a sterile cotton swab against the cheek and gum. It is important to avoid touching the cotton tip of the swab with bare hands to prevent contamination.
For accurate results, individuals should refrain from eating, drinking, brushing teeth, chewing gum, or breastfeeding for an hour before collection. Two swabs are collected from each person participating in the test, one from each cheek, by vigorously scraping and rotating the swab for 30 seconds. After collection, the swabs must air dry for 30 minutes in their specimen envelopes to prevent DNA degradation before being sealed and sent to the laboratory.
Laboratory Analysis
Once samples arrive at the laboratory, DNA is extracted from the collected buccal cells and then amplified using Polymerase Chain Reaction (PCR). PCR creates millions or billions of copies of specific DNA regions to ensure sufficient quantities for analysis.
Following amplification, scientists analyze Short Tandem Repeats (STRs), which are short, repeating DNA sequences located at specific points on chromosomes. The number of these repeats varies significantly between individuals, making them unique genetic markers. By examining STR markers, the DNA profiles of the child and alleged father are compared to identify shared genetic sequences, known as alleles. If the child’s STR profile matches the alleged father’s, it supports a biological relationship.
Interpreting the Results
Paternity test results present two possible outcomes: “exclusion” or “not excluded”. An exclusion means the tested man is not the biological father, indicated by a 0% probability of paternity. This occurs when markers do not match between the child and the alleged father.
If the alleged father is “not excluded,” it means he is considered the biological father, with a probability of paternity of 99.9% or higher. This high percentage indicates the likelihood that the tested man is the biological father compared to a random individual from the general population. Including the mother’s DNA sample can provide clearer results and increase the probability of paternity, though it is not always required for testing.
Different Testing Scenarios
Paternity tests are conducted in various contexts, each with distinct implications. “Peace of mind” or at-home tests are for personal information, and samples can be collected by individuals themselves. While these tests are scientifically accurate, their results are not admissible in court.
In contrast, “legal” or court-admissible tests require strict adherence to a “chain of custody” protocol. This means a third party, such as a medical professional or an authorized collector, must collect the samples to ensure their integrity and prevent tampering. Legal tests are necessary for official matters like child custody, child support, immigration, or birth certificate amendments.
Prenatal paternity testing can also determine fatherhood before a child is born. Non-invasive prenatal paternity (NIPP) tests use a blood sample from the mother and a cheek swab from the alleged father. More invasive methods, such as amniocentesis or chorionic villus sampling (CVS), involve collecting amniotic fluid or placental tissue, respectively, performed by an obstetrician. These invasive procedures carry a small risk of complications, including miscarriage.