During 2018, police cracked 19 cold cases using ancestry testing sites. One of them was the murder of 8-year-old April Tinsley, which took place in the spring of 1988. The secret? Using DNA from the crime scene, obtaining a warrant to upload the DNA to a site called GEDmatch – popular among genealogists – and seeing who comes up as a close match. From there, detectives and genealogists work together to zero in on possible suspects.
DNA profiling wasn’t really standard in American investigations until President George W. Bush signed the Justice for All Act in 2004 – and under that act, it became commonplace for police to stockpile suspects’ DNA found at crime scenes.
Parabon NanoLabs, a private company that scans public DNA profile records submitted on genealogy websites, has been involved in solving several of the cold cases police have brought to them. They’re the ones responsible for tracking down the Golden State Killer.
Police are finding murderers and serial rapists – including the Ramsey Street Rapist from North Carolina and a serial rapist from Sacramento – all by using GEDmatch.
First, they upload the DNA data into the website. Within a few days, the website’s algorithm identifies other users who have similar DNA. Close blood relatives always share some DNA, which is measured in centimorgans. For example, a parent and child share an average of 3,600 centimorgans of DNA. Full siblings share anywhere between 2,300 and 3,900 centimorgans of DNA (twins are on the high end). Half-siblings, aunts and uncles, and grandparents share between 1,300 and 2,300 centimorgans.
Police are able to find those matches and get closer to the suspects they’re looking for – and when there isn’t a close match, they use genealogical tools to track down more potential suspects.
For example, if investigators find a match that shares 750 centimorgans of DNA with the DNA found at a crime scene, they’re looking for that matching person’s first cousins. That lets them zero in on suspects far faster – and far more easily – than traditional investigations would. When they can’t find names and identifying information on GEDmatch, or when they need to zero in more specifically, they turn to other tools like Ancestry.com and 23andMe.
(You can check out the DNA autosomal statistics chart, which breaks down how much DNA relatives share, here.)
What Do You Think?
Have you heard about any of these cases being solved with DNA? Have you uploaded your own DNA data to GEDmatch, Ancestry.com or 23andMe? What would you do if police approached you to ask questions about one of your relatives based on your DNA match?