The rapid expansion of DNA ancestry databases is changing the way we investigate crimes. Earlier this month, police submitted DNA from crime scenes to GEDmatch (one of the many ancestry registries), and it led to the identification of about two dozen alleged killers’ relatives, which allowed police to construct family trees to hone in on the suspects. Larger DNA databases could contain data from about 10 million people, yielding 350 forth cousins and about 200 third cousins. But since 23andMe and AncestryDNA are both private (unlike GEDmatch, which is commercial), police cannot use them to match a suspect’s DNA without a court order. (sciencemag.org)