The second type of DNA database used for law enforcement is a new entrant—the consumer genetics platform. To date, at least two consumer genetics platforms, GEDmatch and FamilyTreeDNA, have publicly acknowledged or embraced working with law enforcement to identify criminal suspects. Proponents of government use of these databases have emphasized that genetic profiles are voluntarily shared on these sites. In other words, because people have volunteered their genetic data, it is OK for law enforcement to use it too.

But the identification of individuals who are not directly included in a genetic database runs afoul of any given reason law enforcement use of such databases is legally and ethically acceptable. These individuals have not previously been arrested or convicted of a crime. Nor have they “volunteered” their DNA on a consumer genetics platform. Instead, like millions of ordinary Americans, these individuals are identifiable to police through the genetic data of their kin. Few genetic relationships, however, are voluntary. Even if parents can be said to voluntarily choose to have children, children plainly do not choose their parents. Nor do we choose our siblings, cousins, or more distant relatives—if we even know who they are.

And the reach of these genetic databases, combined with identifiability-by-relatedness, is rapidly growing. Law enforcement will soon have access to enough genetic profiles to reach nearly all Americans of European descent, if they don’t already.