Some states take DNA from anyone arrested. But they can search for family members (California approved this in 2010 I think). They caught the "Grim Sleeper" p

Some states take DNA from anyone arrested. But they can search for family members (California approved this in 2010 I think). They caught the "Grim Sleeper" partially because his son got arrested for a Felony. https://en.wikipedia.org/wiki/Grim_Sleeper https://en.wikipedia.org/wiki/Grim_Sleeper "Franklin was identified at least in part on familial DNA analysis.[41] Police had found no exact match between DNA found at the crime scenes and any of the profiles in California's DNA profile database, so they searched the database for stored profiles that demonstrated sufficient similarity to allow police to infer a familial relationship. They found similar DNA belonging to Franklin's son, Christopher, who had been convicted of a felony weapons charge in 2008. Christopher was too young to have committed the murders, but the familial DNA match led investigators to look at his father, Lonnie, as the likely perpetrator.[42]"