Suppose two people are located in the United States and they wish to prove they are related through DNA testing.

They want the test results to be admissible in court so they must use certified labs with chain of custody (rather than Ancestry.com or similar).

Also suppose the two people live 1500 miles apart, so it is not easy for them to both go to the same test facility.

Is it common to gather the DNA samples at two separate test labs and have one of the labs either send the raw sample or the results to the other lab to generate the report? Or is there some other method commonly used that preserves chain of custody? In other words, how would a court normally specify this be done?

  • 2
    In what context would a court specify how a genetic test is to be conducted?
    – user6726
    Sep 5, 2020 at 0:59
  • @user6726 I don't know. But there must be some guidelines or at least common practice for how this is handled.
    – user4574
    Sep 5, 2020 at 1:05
  • Let's start with a simpler problem: why do the courts care if two people are genetically related? I can't think of any reason at all.
    – user6726
    Sep 5, 2020 at 1:22
  • @user6726 The courts may care in determining inheritance of property after someone's death for one. A biological child can inherit property, but its possible that paternity could be in dispute after death. The other would be payment of child support. From what I understand, people are only required to pay child support for their biological children. The other would be that family courts often preferentially place orphans with relatives, but the relation between two people could be in dispute. In petitions for custody, one must have standing to file. Being a relative gives standing.
    – user4574
    Sep 5, 2020 at 3:52
  • @user4574 courts have regularly found that non-biological children are to be covered by child support if the parent paying the support has accepted them as their own. Plenty of cuckold cases have ended up with the estranged husband having to pay support for someone else's child in full knowledge of that being the case.
    – user28517
    Sep 6, 2020 at 1:32

1 Answer 1


Generally, the courts don't care about who is genetically related to who, but establishing paternity is a special case. The specifics are governed by state law, here is what Washington does. Under the Uniform Parentage Act, when there is a legal dispute as to parentage ("is X a parent of Y?") and X either volunteers for genetic testing, or is tested under order of the court or a child support agency, then the courts and the law gets involved in genetic testing. Testing cannot be used to challenge the parentage of an individual legally established to be a parent in other ways, or to establish the parentage of a donor. There are prerequisites to the court ordering a test, for example a party may make a sworn statement that there is a reasonable possibility that X is the child's genetic parent, or swears that it's reasonable that the person is not a genetic parent.

Assuming the court issues an order, then RCW 26.26A.315 governs the procedures for the testing. As for the qualifications of the lab and test, the requirement is that

(1) Genetic testing must be of a type reasonably relied on by experts in the field of genetic testing and performed in a testing laboratory accredited by: (a) The AABB, formerly known as the American association of blood banks, or a successor to its functions; or (b) An accrediting body designated by the secretary of the United States department of health and human services.

and the sample requirements are

(2) A specimen used in genetic testing may consist of a sample or a combination of samples of blood, buccal cells, bone, hair, or other body tissue or fluid. The specimen used in the testing need not be of the same kind for each individual undergoing genetic testing.

Then there are procedures regarding resolution of disputes of ethnic parameters for computing the relationship index, including changing labs.

Nothing in the law itself states how the samples are to be processed: that is implicit in the accreditation requirements of AABB, and to be legally admissible, chain of custody protocols must be observed for collecting and processing. Chain of custody is a general requirement for evidence and there isn't anything special about genetic testing, see here for an overview and here for some nuances (e.g. the importance of having technically-competent and accurately-documented collection of samples). If the sample is inadmissible because of broken chain of custody, then the court can order another sample be taken.

  • So I guess the law says that the samples must be taken and processed by experts without going into the details of how (I guess its reasonable to leave that to the experts). But in the case where the people are submitting the samples can't get to the same testing site (even if there is no law regarding that situation) there must be some way (or ways) this is usually handled beyond the judge just saying "make it happen". That's really the heart of my question.
    – user4574
    Sep 6, 2020 at 21:31
  • I don't know if there is a technical reason for the two samples to be physically in the same location, do you?
    – user6726
    Sep 6, 2020 at 23:25
  • It depends on how they are processed. Typically one doesn't sequence the entirety of someone's DNA. They pick a subset of genes to search for. If each lab processes them separately then each lab must look for genes on the same list. That means there either needs to be a standard list, or the labs need to collaborate somehow. Also the results must be in a form that is directly comparable with one another between labs. On the other hand, if one lab just mails the sample to the other lab then the other lab can do whatever they want once they get both samples.
    – user4574
    Sep 7, 2020 at 0:28

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