What Is a Paternity Test and How Does It Work?

When there is a genuine question about who a child's biological parent is, genetic testing can provide a clear answer. In Washington family law cases, that testing follows specific rules about when a court can order it and how the results are handled. This topic is part of Washington paternity law.

What a Paternity Test Actually Is

A paternity test, more precisely called genetic testing, compares DNA samples to determine whether a particular person is a child's genetic parent. Every person inherits half of their genetic material from each biological parent, so a laboratory can compare markers in the child's sample against the alleged parent's sample and calculate the likelihood of a biological relationship. Modern testing is highly accurate and can either confirm a genetic link with a very high probability or exclude it entirely. Related guides cover What Is Genetic Testing for Paternity? and How Do I Get Court-Ordered Paternity Testing?.

Collecting the sample is simple and painless. In most cases the laboratory uses a cheek swab, a soft applicator rubbed inside the mouth to collect cells, rather than drawing blood. The samples from the child and the alleged parent are then analyzed and compared. Washington's Uniform Parentage Act, chapter 26.26A RCW, contains a full subchapter governing this process, found at RCW 26.26A.300 through 26.26A.355.

When a Court Can Order Genetic Testing

You cannot compel someone to take a DNA test simply because you are curious. Washington law sets a threshold. Under RCW 26.26A.310, in a proceeding to determine parentage the court shall order the child and any other individual to submit to genetic testing if the request is supported by the sworn statement of a party. That sworn statement must either allege a reasonable possibility that the individual is the child's genetic parent, or deny genetic parentage while stating facts establishing a reasonable possibility that the individual is not a genetic parent, RCW 26.26A.310.

The phrase reasonable possibility is the key. The law requires more than a bare accusation or a hunch. A party asking for testing has to swear, under penalty of the law, to facts showing a genuine basis for the request, whether that party is trying to establish parentage or trying to rule it out. The requirement cuts both ways, protecting people from being dragged into testing on nothing more than speculation.

The statute also addresses some practical points. A child support agency can order genetic testing only when there is no presumed, acknowledged, or adjudicated parent other than the woman who gave birth, RCW 26.26A.310. Testing of the woman who gave birth is not required before the child and the alleged parent can be tested, so if she is unavailable or declines, the court may still order testing of the child and each person whose parentage is being decided. And no one may order in utero genetic testing, meaning testing before birth. An order for genetic testing is enforceable by contempt, so a person who refuses a valid order faces real consequences.

Limits on Ordering a Test

The court's power to order testing is not unlimited. Where a child already has a presumed parent, or where someone claims parent status based on their relationship with the child, or where an existing acknowledgment of parentage is being challenged, the court may deny a request for genetic testing after weighing certain statutory factors, RCW 26.26A.310. This reflects an important principle in Washington law. Sometimes the child's existing family relationships and stability matter more than establishing a biological link, and the law gives judges room to protect a child from having a settled parental bond disturbed by testing. If a person is already legally barred from establishing parentage, the court must deny the testing request altogether.

How the Results Are Used

Once testing is done, the results have to be documented in a reliable way to count in court. A report of genetic testing must be in a record and signed under penalty of perjury by a designee of the testing laboratory, and a compliant report is self-authenticating, RCW 26.26A.320. The law also spells out the chain-of-custody documentation that makes results admissible without live testimony, including the name and photograph of each person tested, who collected each sample, where and when it was collected, and who received it at the lab, RCW 26.26A.320. These safeguards exist to make sure the samples were not switched or tampered with, so the court can rely on the numbers.

Cost is handled by statute as well. Payment for initial genetic testing must be made in advance, by a child support agency where it is providing services, by the person who requested the testing, as the parties agree, or as the court orders, RCW 26.26A.330. If a child support agency pays, it may later seek reimbursement from the genetic parent whose relationship to the child is established.

Why the Result Matters

A confirmed genetic result can be the foundation for establishing legal parentage, which in turn opens the door to a parenting plan, residential time, decision-making authority, and both the right to seek and the obligation to pay child support. For parents in Snohomish County facing an unresolved parentage question, genetic testing is often the step that finally brings clarity to everything that follows.

Because the timing and procedure of testing can affect the outcome, and because a request can be granted or denied depending on the facts, these matters are worth handling carefully. If you have questions about establishing or disputing parentage through genetic testing, the Law Office of Chad Foster can walk you through your options. Reach out to talk about your situation.