I have to admit I have *no* idea what the numbers actually are. But I'm certain that none of my immediate family, and none of my wife's immediate family, have been genotyped for any reason. I don't know of any of our friends or coworkers who have been typed, though I can't be certain of all of them. Is DNA typing for non-forensic reasons really so common?
OK, maybe you are in the field (e.g., military) where it is not common to genotype relatives. But look at it in this way: you might have relatives, second cousins, who are not even close to you, are into genealogy and have done the genetic studies.
I am an emigrant and never thought I had relatives here. Guess what? Found two, on one line but close enough to me, if I left my DNA at a crime scene, whether typed or not, I could be found via these relatives whom I never saw in my life.
Same applies to you. You can’t call all your cousins and forbid them to do genealogy tests. So even if you have never been typed, but left your DNA at a CS (sorry!) ), all that the Parabon needs is to run yours, unknown, against the database and find relatives.
Of course, there might be complications. For example: the criminal might be the product of egg or sperm donation. Then, maybe, there are relatives, but no established connection on the genealogy tree. It might well be the case. Or, the tree might be wrong; some have many non-paternity events.
Now, about the genetic tests. They were super popular around 2015, when I randomly did mine, more in the context of a FB joke. But that brought me to the site where lots of people posted. There were two groups, one interested in ethnicity (“who am I?”) and the other one, in health, as the tests could be downloaded to Promethease that could tell you all potentially hazardous genes.
And then, people cross-uploaded their DNAs to other ancestry sites, to meet more relatives…
Suffice it to say, if your ancestors are from Western Europe, especially, Britain, they can say what county your ancestors were from.
Now, this is exactly what is undermining our commercial ancestry companies now. The first people to be tested were highly endogamous groups (e.g., Ashkenazi and Finns), and then, people from Western Europe. The first comers.
The companies seemingly did not foresee that our Asians, Indians, African Americans would, too, want to know their roots. And now, people who are of mixed heritage, might get such humiliating responses as: half of their genome is explained up to the ancestral town in Ireland, the other 50% is “India and Pakistan” (thank you, “23 and me”! Luckily, there is WeGene, Asian site, that reads all Caucasian as “British”, but is very good with Asian database).
It is getting better, but if our criminal is a mixture, with less examined genome on maternal side, and he left only a hair, hence, mitoDNA, there may be no match.
Or, if he has Y from a yet-unexplored group (could be Native Americans, could be lots of ethnicities), there, indeed, may be no matches.
I can dwell on it for ages, as I have seen both situations in my family (too rare is bad, too common is worse, a common with a private mutation is bad, DNA not linked to a tree is bad…you name it!).
