What are mirror trees, please?
Good points about this man possibly being non-biological to parents. I suspected that a while back.
Mirror trees, the way I understand, is how they investigate old crimes. They put the DNA in the format compatible with Gedmatch database. If they are lucky, they find at least one close enough relative. (2nd cousin would be great). Or maybe, several not so close but still workable. Then they reconstruct the family trees for these matches, upwards, and compare them. Somewhere, depending on the proximity, they will arrive at the potential common ancestor (s). And from the ancestor, they go back to all his descendants and find the one that would potentially match the profile. (e.g., living in the same area, Delphi or vicinity, for this case), being around in the time of the murders, or fitting the profile otherwise. Usually there might be 3-4 people who could be the potential POI from the DNA studies, so they don't necessarily zero in on one person. Then they might ask the DNA from all 3-4 to confirm. This is when someone refusing a swab would be interesting...
It works better with old crimes. When you have the DNA, the area of the crimes, but nothing else. This is how the first crime in California was solved. They identified 3-4 people and collected their DNA (discarded tissues, glasses, etc).
Please correct me if I am wrong. I never worked with mirror trees as I am from another country and once missed a huge window of opportunity.
In the case when there is fresh DNA, and some other clues, one could simply collect the DNA from potential suspects, or a larger group of people. But after all, the POI might know he is of interest, and be very wary of leaving any "traces" anywhere. Then you have to work the same way.
What I am concerned about is that if there was embryo donation, or international adoption, the situation is much worse. Also, non-paternity event is confusing.
But - for international adoptions, at least, there might be traces of an adoption. People can't adopt that covertly.
For embryo donations, that always are a possibility, as they were around since mid-80es, one would hope that the donors were from the same area, and then one could eventually find them. But it is more straightforward if the person is not adopted.
This is how I understand it. Tell me if I am wrong.