You have likely seen the Golden State Killer and many other cold cases solved recently through the use of genetic genealogy. But how does genetic genealogy for law enforcement work exactly? First an autosomal DNA profile of the assailant in your cold case is generated through forensic testing of crime scene evidence that contains your assailant's DNA. Once this profile is generated it is then converted to a file format that can be uploaded to a public genetic genealogy database such as GEDmatch. After processing, the database then returns a list of DNA matches of people who are related to your assailant. These matches can vary from as close as parents, siblings, aunts and uncles, to matches as distant as 4th cousins and beyond. Predicted relationships between these matches and your suspect can be determined based on the amount of DNA they share. Family trees are then built out for these matches using a combination of standard genealogical methods as well as gathering data from proprietary investigative databases, social media, and public records. By determining where the family trees of DNA matches intersect, it is possible to determine ancestors (both recent and distant) that are shared between your assailant and their DNA matches. Each DNA match adds a bit more to the puzzle, until the search is eventually narrowed down to a potential candidate for your assailant. Law enforcement will then generally collect a discarded DNA sample from the candidate and compare it directly to the crime scene DNA to confirm the match.