Getting a paternity test involves collecting DNA samples (usually a simple cheek swab), sending them to an accredited lab, and receiving results that confirm or rule out a biological relationship. The process is straightforward whether you order a kit online or visit a clinic, but the type of test you choose determines whether your results can be used in court.
Home Kits vs. Legal Tests
Paternity tests fall into two categories: “peace of mind” home tests and legally admissible tests. The DNA science behind both is identical, but the paperwork and collection process differ significantly.
A home paternity test kit costs between $100 and $300. You order it online or buy it at a pharmacy, collect the samples yourself at home, and mail them to a lab. The results are accurate, but because no neutral third party verified who provided the samples, they carry no legal weight. You can’t use them in court for child support, custody, or inheritance disputes.
A legal paternity test costs $400 to $800 or more and requires what’s called “chain of custody.” This means a trained collector (at a clinic, lab, or hospital) verifies each person’s identity with a photo ID, witnesses the sample collection, photographs the participants, and seals everything with tamper-evident tape. Every step is documented so the results hold up in court. If a court orders the test, both parties receive an appointment date at a designated lab.
How the DNA Sample Is Collected
The standard method is a buccal swab, a soft foam-tipped or cotton-tipped applicator rubbed against the inside of your cheek. It’s painless and takes about 30 seconds per person. Both the child and the potential father need to provide samples. Including the mother’s sample isn’t required but can strengthen the analysis.
The collector places the swab tip inside the mouth and rubs it firmly against the inner cheek for at least 10 seconds per side, pressing hard enough that you can see the outline of the swab from the outside of the cheek. The goal is to collect loose cells from the cheek lining, which contain a full copy of your DNA. With some collection methods, the swab is then pressed onto a special card that preserves the DNA. With others, the swabs are placed back into their packaging and air-dried completely before being sealed in a paper envelope for transport.
A few practical tips to get a clean sample: avoid eating, drinking, smoking, or chewing gum for at least 30 minutes before the swab. For infants, wait at least an hour after breastfeeding. These precautions prevent food particles or another person’s DNA from contaminating the sample.
What Happens at the Lab
The lab extracts DNA from the cheek cells and examines specific genetic markers called short tandem repeats (STRs). Modern labs typically analyze 21 to 24 of these markers. A child inherits one copy of each marker from their biological mother and one from their biological father, so the lab looks at each marker in the child’s profile and checks whether the potential father carries a matching version.
If the tested man is excluded as the father, the result is definitive. Multiple markers won’t match, and there is zero probability of paternity. If the man is included as the father, the lab calculates a Combined Paternity Index, which expresses how much more likely it is that this man is the biological father compared to a random unrelated man. Labs in the United States generally require this index to exceed 100 before confirming paternity, while European labs set the threshold at 1,000. In practice, positive results almost always show a probability of paternity above 99.9%.
Most labs return results within 3 to 5 business days after receiving the samples, though some offer rush processing for an extra fee.
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 the 7th week of pregnancy. It works because fragments of the fetus’s DNA circulate in the mother’s bloodstream. A lab draws a standard blood sample from the mother, isolates that fetal DNA from her plasma, builds the fetus’s genetic profile, and compares it to a cheek swab from the potential father.
NIPP is the safest prenatal option because it poses no risk to the pregnancy. Older methods, still technically available, are invasive. Chorionic villus sampling (CVS), performed between weeks 10 and 13, carries a miscarriage risk of 0.5% to 1%. Amniocentesis, done between weeks 15 and 18, has a miscarriage risk of 0.25% to 0.5%. Given these risks, the non-invasive blood test has largely replaced both for paternity purposes.
Testing Without the Father
If the potential father is unavailable, unwilling, deceased, or otherwise inaccessible, several alternative tests can establish a biological link indirectly.
- Grandparent test: Compares the child’s DNA to one or both of the alleged father’s parents. Accuracy improves significantly when both grandparents participate and the mother’s sample is included.
- Sibling test: Compares DNA between two people to determine whether they share a parent. Full siblings share roughly 50% of their DNA, while half-siblings share about 25%.
- Avuncular (aunt/uncle) test: Determines whether a child is biologically related to a sibling of the alleged father.
- Forensic sample test: Uses DNA recovered from personal items like a toothbrush, razor, hair with roots, cigarette butts, or clothing stains. Success depends entirely on the quality of the sample, and not every item yields usable DNA.
These indirect tests are less conclusive than a standard paternity test. The more relatives who participate, the stronger the statistical conclusion.
Choosing an Accredited Lab
Whether you’re ordering a home kit or scheduling a legal test, check that the lab holds accreditation from the AABB (formerly the American Association of Blood Banks). AABB accreditation means the facility has been independently assessed for accuracy and quality in relationship testing. Courts and immigration authorities, including USCIS, require results from AABB-accredited labs.
Accreditation information is usually listed on the lab’s website or the test kit packaging. If you can’t find it, ask before you pay. An unaccredited lab may still produce accurate results, but those results are far more likely to be challenged or rejected if you ever need them for legal purposes.
Keeping Your Sample Intact
DNA on buccal swabs is surprisingly stable. Properly collected samples stored at room temperature remain viable for up to 80 days, and they ship without any special cooling. The key rules: let the swabs air-dry completely before sealing them (moisture promotes bacterial growth that degrades DNA), use paper envelopes rather than plastic bags (paper allows residual moisture to escape), and never freeze the samples. If shipping is delayed, refrigeration is acceptable as a precaution.