Tag: Forensics

The genetic future is here when it comes to finding relatives of suspects

Posted on by Razib Khan

You may have heard that a suspect was arrested who is alleged to be the “Golden State Killer.” DNA played an important role, Relative’s DNA from genealogy websites cracked East Area Rapist case, DA’s office says.

I think Alexander Kim’s supposition is probably right. It wasn’t a direct to consumer company that you know of that uses a genome-wide analysis, but probably old-fashioned Y STR matching which allowed the researchers to converge on the suspect. The public databases for this are extensive enough now that they might yield something, and law enforcement is comfortable with STR tests. This is really a preview of what’s to come. If researchers routinely extract DNA from remains that are tens of thousands of years old it seems clear that a lot more material will come out of old rape kits.

That’s one dimension. The other dimension is that we have many more markers to work with now. Even without whole-genome analysis, you can identify relatives with reasonable precision out to 2nd cousins (it gets a little dicier beyond that).

But the most important variable happens to be with numbers. If you read Alon Keinan’s piece, Crowdsourcing big data research on human history and health: from genealogies to genomes and back again, you know that probably nearly 20 million people have taken advantage of genome-wide consumer testing. Assuming 10 million are in the United States, a substantial number of “cold cases” could probably be closed by just looking for matches within these databases and establishing the pedigrees which suspects come from.

Of course, the genomics companies are not just going to open their databases to law enforcement.  But I’m not sure that that will be necessary. There are enough genealogy enthusiasts that public forums and services to facilitate matches will probably suffice. If only a few percent of the American population is in these forums, then that might get us 90% of the way there.

Addendum: There has been some work in forensic genetics “predicting” physical appearance. A lot of this is not primetime, but one area where a lot could be done: fine-scale ancestral analysis. Using haplotype-based methods and looking for matches within public datasets one could probably narrow down the ethnic background of a suspect pretty well from DNA. If the test tells you someone is Northern European in Minnesota that might not help, but if it tells you that they are around half Lithuanian, that might be very useful….