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 over 200,000. 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.
In a statement to WIRED, Carson Colvin, a spokesperson for the city of Tulsa, called GEDmatch the “best option available for connecting the undocumented remains buried at Oaklawn Cemetery with their living family members.” Colvin points out that GEDmatch has different levels of privacy settings, including one that allows users to opt out of law enforcement searches. Users can also change these permissions whenever they choose, or delete their profiles altogether.
City officials may eventually be informed of the names of relatives that closely match with the unknown bodies, but they won’t have access to individuals’ DNA samples or their raw data files. GEDmatch also does not hold raw data files, according to Brett Williams, CEO of Verogen, the forensics company that owns the database. “All data in GEDmatch is encoded upon upload, and the initial raw data is subsequently deleted,” he says.
