A paternity test requires a DNA sample from the potential father and the child, and in some cases the biological mother. The standard sample is a simple cheek swab, collected by rubbing a cotton swab along the inside of the mouth to gather cells. Beyond the biological samples, what you need depends on whether the test is for personal knowledge or legal purposes.
DNA Samples: What Gets Collected
The vast majority of paternity tests use buccal (cheek) swabs. You press a cotton-tipped swab against the inside of your cheek, rotate it for about 30 seconds, and the swab picks up enough cells to extract a full DNA profile. It’s painless and takes under a minute per person. Both the potential father and the child provide swabs this way.
Including the biological mother’s sample isn’t always required, but it strengthens the results. Her DNA helps the lab isolate exactly which half of the child’s genetic markers came from the father’s side, making the comparison cleaner and more definitive.
In some situations, a blood draw replaces the cheek swab. This is more common in prenatal testing or when a lab needs a higher quantity of DNA. For a standard post-birth test, though, cheek swabs are the industry norm.
Home Tests vs. Legal Tests
If you only need an answer for yourself, an at-home paternity test kit is the simplest option. You order a kit online, it arrives in about two to three business days, and you collect the cheek swabs at home. You then mail the samples back to the lab. These results are not admissible in court.
A legal paternity test requires something called chain of custody. This means a neutral third party, typically a trained collector at an approved lab or collection site, must verify the identity of each person being tested, witness the sample collection, and document the entire process. You’ll need to bring a government-issued photo ID, and the collector may photograph each participant. For children, a birth certificate is typically required. Every sample is sealed, labeled, and tracked from the moment it’s collected until it reaches the lab. This documentation is what makes results valid as evidence in court proceedings like custody cases, child support disputes, or immigration applications.
In some states, additional steps apply. New York, for example, requires a written request from a physician or court order before legal testing can proceed.
Prenatal Paternity Testing
You don’t have to wait until a baby is born. A non-invasive prenatal paternity test (NIPP) can be performed as early as seven weeks into pregnancy. It works because fragments of the fetus’s DNA circulate in the mother’s bloodstream. The lab draws blood from the mother and collects a cheek swab from the potential father, then compares the fetal DNA in the blood sample against the father’s profile.
NIPP carries no risk to the pregnancy because only a standard blood draw from the mother is involved. Older prenatal methods, amniocentesis and chorionic villus sampling (CVS), use a thin needle to collect fluid or tissue from inside the uterus. Amniocentesis is performed between 15 and 20 weeks, while CVS can be done earlier in pregnancy. Both carry a small risk of complications, so NIPP has largely replaced them for paternity purposes.
When the Father Isn’t Available
If the alleged father is deceased, missing, or unwilling to participate, testing can still move forward using alternative approaches. Sibling DNA testing compares the child’s DNA to that of the alleged father’s other known children to determine whether they share the same biological father. Grandparent testing works similarly, using DNA from the alleged father’s parents as a reference point. These indirect tests are less definitive than a direct father-child comparison, but they can still produce meaningful results, especially when the biological mother also provides a sample.
Some labs also accept what are called forensic or non-standard samples. These are everyday items that carry someone’s DNA: a used toothbrush (used at least 20 to 30 times), hair strands with the root still attached, nail clippings, earwax, or chewed gum. Labs run a viability test first to confirm there’s enough usable DNA on the item before proceeding. The success rate varies by sample quality, and if the DNA turns out to be insufficient, you may face an additional fee (around $100) to submit a new sample. These options exist for situations where a cheek swab simply isn’t possible, but a standard swab will always give the most reliable starting material.
How Results Work
Paternity test results come back as either an inclusion or an exclusion. An inclusion means the tested man is not excluded as the biological father, and the report will list a probability of paternity, typically 99% or higher for a true biological match. That 99% figure reflects the statistical likelihood that the tested man is the father compared to a random, unrelated man from the same population. An exclusion means the DNA profiles do not match, and the tested man is definitively not the biological father.
Accuracy depends partly on how many genetic markers the lab analyzes. The industry standard is 16 markers, but some labs test more. A higher number of markers produces a more precise result, so if you’re comparing at-home kits, the number of markers analyzed is worth checking.
What to Prepare Before You Test
For a home test, all you need is the kit, the participants, and about 30 minutes. Avoid eating, drinking, or smoking for at least 30 minutes before collecting a cheek swab, as residue in the mouth can contaminate the sample.
For a legal test, gather the following before your appointment:
- Government-issued photo ID for each adult being tested (driver’s license, passport, or state ID)
- Birth certificate for any child being tested
- Court order or physician request if required by your state
- Payment at the time of collection, since most labs require upfront payment before processing
Legal collections are scheduled through the lab, so you’ll coordinate a time for all participants to appear, sometimes at the same location, sometimes separately. The lab handles the rest once samples are sealed and sent.