How a legal paternity test works in California

Legal vs private in one paragraph

Both tests go to the same independent AABB-accredited laboratory and produce the same kind of report, with a probability of paternity. A private test takes your word for who was swabbed, which is fine for your own knowledge and useless to a judge. A legal test adds an identity and custody record at every step, so a third party can trust that the report is about the people named on it. That record is called the chain of custody.

The chain-of-custody procedure, step by step

1. Identity. Every adult presents government photo ID, which is verified and copied onto the case file. For a child, the consenting parent or guardian presents theirs, plus the child's birth certificate if available.
2. Neutral collector. The samples are collected by a neutral collector with no connection to anyone being tested, following the laboratory's procedure. Participants never handle the kit before or after collection and never ship their own samples.
3. Witnessed collection. Each cheek swab is taken in front of the collector, labeled with the participant's details, and signed by the participant.
4. Photograph and thumbprint. The laboratory's procedure typically records a photo and a thumbprint of each participant on the custody form.
5. Tamper-evident sealing. Samples are sealed in the laboratory's packaging in front of you. Broken or missing seals on arrival void the case.
6. Custody form. A chain-of-custody form listing who was tested, who collected, when and how, travels with the samples and stays on file at the laboratory.
7. Tracked overnight shipping to the laboratory, which logs receipt and checks the seals against the form.
8. The report. A notarized hard copy is mailed to the address on the custody form, with a PDF. It states the probability of paternity and the combined paternity index, identifies the laboratory and its accreditation, and references the custody record.

Miss any step, for example a father who swabs himself at home and mails it in, and there is no chain of custody, no matter how good the laboratory is. That is why a private result cannot be upgraded to a legal one later; the samples have to be recollected.

Consent for a child under 18

• A parent or legal guardian with authority to consent must attend and sign for the child.
• If the parents are not married to each other, the child's mother consents. This is the rule the laboratory applies on every case, because until parentage is established the mother is the child's recognized legal parent.
• A court order directing the test can take the place of the mother's consent. Bring it.
• An adult being tested always consents for themselves. Nobody is tested without their knowledge, and samples from personal items are never accepted.

Sort consent out before you book. Without it the laboratory will not process the child's sample and the appointment is wasted.

When people in California use a privately arranged legal test

• Before anything is filed. Two parents who want certainty before signing a Voluntary Declaration of Parentage, agreeing on support, or deciding whether to go to court at all.
• On an attorney's advice. A family-law attorney may ask for chain-of-custody testing to support a filing, a settlement, or a mediation.
• For an agency or benefits request that asks for accredited, chain-of-custody DNA testing, for example some survivor-benefit, inheritance, or records matters. Ask the agency exactly what it requires first.
• Personal certainty with the option kept open. Some people choose the legal test simply so the result can be used later if it ever has to be.

When the court arranges the test instead

California courts can order genetic testing in a contested parentage case (Family Code section 7551 and following). In a child support case opened with the county's Department of Child Support Services, the agency typically arranges the genetic testing itself, through its own contracted laboratory, and may cover the cost up front. In those situations a test you buy privately may not be accepted in place of the court's or agency's own process, or may have to be repeated.

What a paternity test does not do

• It does not by itself establish legal parentage. In California that is done by a Voluntary Declaration of Parentage or by a court order. A test result is evidence that may support either one.
• It does not change a birth certificate. Amendments go through the state's vital records process or the court, and they have their own requirements.
• It does not set or change child support or custody. Those are court decisions.
• It is not a "court-approved" or "guaranteed accepted" document. No privately purchased test is guaranteed to be accepted in every proceeding. Acceptance is always the decision of the court or agency involved.

Questions about what a result means for your matter go to an attorney or the court. We will tell you which test you need, who has to attend and what to bring, and we stop there.