The argument against, stated at its strongest, is that the people who uploaded their DNA to GEDmatch did not consent to law enforcement use, and their lack of explicit objection cannot be construed as consent to a use they were not told about. Their genetic data represents not only their own information but also partial genetic information about all of their relatives, who may never have used any genetic testing service and whose privacy interests are implicated by others’ decisions to upload.
Some scholars have argued that the consent problem is more fundamental than the violent-crimes restriction addresses: that even for violent crimes, the use of genetic data submitted for unrelated purposes without the knowledge of those whose data is used is a form of appropriation that requires explicit authorization. Others have argued that the law enforcement use of a publicly accessible database, one that any member of the public with a DNA file can access, does not implicate the same privacy interests as sealed records or private communications.
The legal challenges to evidence obtained through investigative genetic genealogy have begun to work through the court system. Defendants have raised Fourth Amendment challenges, arguing that the genealogical search constituted a warrantless search. Courts that have addressed these challenges have generally rejected them, relying on the principle that individuals have no reasonable expectation of privacy in data voluntarily shared with third parties. But the legal questions are not fully resolved.
The debate will continue, informed by the cases that the method resolves and the ones it does not, by policy choices of legislatures and courts, and by the evolving understanding of what genetic privacy means in a world where genetic data is routinely shared through consumer services.