[consteval]

Food for thought, they found the Golden State Killer using the DNA of a third cousin. So in a familial pool of hundreds of people, if even 1 gives up DNA then you could (with effort) find out anyone else. Provided they're in a good spot on the tree, you can't do much with a 5th cousin.

Of course the Golden State Killer was extenuating circumstances. He killed about a dozen people and sexually assaulted over 50 women in the 70s. But, it makes you wonder about the future of criminology.