Forensic genealogy has a starring role in media reports about the apprehension of Idaho quadruple murder suspect Bryan Kohlberger. The reported match of DNA evidence collected from a button snap on a knife sheath left at the murder scene to a sample taken from the suspect’s father’s trash in Pennsylvania demonstrates how far the field of forensic genetics has come in the last few decades, says Northeastern University criminologist James Alan Fox. But Fox says that while forensic genealogy is a powerful tool, its usefulness in the majority of homicide investigations is limited—and probably wasn’t even necessary in the Idaho case.
Forensic genealogy is when law enforcement couples DNA analysis with traditional genealogy research to come up with leads for unsolved violent crimes, according to the U.S. Department of Justice. Advances in DNA technology and the proliferation of ancestry DNA research databases have made forensic genealogy a powerful tool in solving cold case crimes, perhaps most famously with the arrest of Joseph James DeAngelo in 2018 for the decades-old Golden Gate killings in California. Investigators used DNA samples taken from the crime scenes to compare against DNA sequences in a public database to help narrow down DeAngelo as a suspect, eventually fishing a tissue out of DeAngelo’s rubbish to make a match.