But this is far from the first time family members’ genetic material has been used to put names to unidentified remains. Scientists around the world have used DNA to identify missing persons and victims of war, genocide, and natural disasters. The International Commission on Missing Persons, or ICMP, an intergovernmental organization based in The Netherlands, has conducted several DNA profiling efforts, including in the Western Balkans, to identify Muslim men and boys killed in the 1995 Srebrenica genocide during the Bosnian War. In these cases, scientists typically invite close family members of the missing to provide blood samples; then they create DNA profiles from the samples, to be compared to those obtained from remains.

The organization’s testing method focuses on a type of DNA variation called short tandem repeats, or STRs. By contrast, consumer tests analyze people’s genetic code by looking at single nucleotide polymorphisms, or SNPs, single-letter changes in DNA sequences that make people unique. STRs are useful in determining closer relationships, whereas SNPs are more stable genetic markers that can be used to establish more distant relationships.

There’s another important distinction between the two approaches, says Kieren Hill, DNA laboratory manager for ICMP: “The difference with what we do is that our data is stored on our own servers.” The organization’s database is private and cannot be accessed by law enforcement. By contrast, GEDmatch is an online piece of software that can be used by anyone, including law enforcement agencies investigating certain violent crimes.

That’s the reason for Miller’s privacy concerns. Miller says adding more Black profiles to the database will create more opportunities for law enforcement to investigate Black people—for example, if police use the GEDmatch profiles to connect the relatives to DNA found at modern crime scenes. “It’s not just yourself that you’re putting at risk. It’s your parents, your cousins, your children, your unborn descendants, your whole family tree,” he says.

Even for people who have never committed a crime, there are risks to uploading genetic data to a public website. Crime scene DNA samples are not necessarily from perpetrators—they could be left by innocent bystanders. Or a person may be a sufficiently close match to get swept into an investigation, even if they are actually only a relative of the person who was involved.

But GEDmatch has its benefits. It contains the profiles of more than 1.3 million people, whereas ICMP has collected around 120,000. The more profiles available, the higher the likelihood that researchers will be able to identify the Tulsa victims. “It’s the most powerful tool available,” says Hellwig.

It’s also more likely to match distant relatives. The Tulsa massacre happened a century ago, and the victims’ descendants may now be living anywhere. The GEDmatch database is international, and it relies on SNP matching, which works for these looser connections.

The ICMP, by contrast, works on more recent events in specific geographic areas; in many cases, there are living family members who can provide samples. For the STR testing the group uses, three reference samples are typically needed from a parent, child, or sibling of a missing person to make a match. With few first-degree relatives of Tulsa victims still alive, that kind of matching isn’t possible.

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