In the US, enough people have submitted DNA to 23andMe, Ancestry, GED match, etc., that a random DNA sample can be identified by so-called “genetic genealogy” methods.
Basically because your generic relatives have submitted their DNA to these services, a small pool of potential candidates for your DNA can be identified, and traditional investigation methods can identify you in that pool.
As the density of people who have submitted DNA to these services increases in the total population, identifying random samples will be easier. (It is already getting easier.)
These techniques were publicized with the Golden State Killer case but have been used in several other law enforcement investigations.
My contact with this field is mostly through friends in the industry, but The Daily podcast’s series on it seemed like a good introduction:
Basically because your generic relatives have submitted their DNA to these services, a small pool of potential candidates for your DNA can be identified, and traditional investigation methods can identify you in that pool.
As the density of people who have submitted DNA to these services increases in the total population, identifying random samples will be easier. (It is already getting easier.)
These techniques were publicized with the Golden State Killer case but have been used in several other law enforcement investigations.
My contact with this field is mostly through friends in the industry, but The Daily podcast’s series on it seemed like a good introduction:
https://www.nytimes.com/2019/06/06/podcasts/the-daily/dna-ge...