by Josiah Himmelman | Feb 18, 2022 | Commentary |
From 1975-1986 the notorious Golden State Killer committed 12 murders, 45 rapes, and 120 burglaries across 6 California counties. These crimes remained unsolved until 2018 when police arrested Joseph DeAngelo, a 73 year old United States Navy Veteran and police officer, in his home in Citrus Heights, California. DeAngelo’s crimes were finally solved after all of these years through the use of a novel forensic technology: familial DNA search (FDS). In a traditional DNA search, law enforcement gather DNA material left at a crime scene. They then test that sample to see if it matches the DNA of anyone in a vast database of known offenders, like the FBI’s combined DNA Index System (CODIS), who have previously provided a DNA sample. This type of search couldn’t help solve DeAngelo’s murders though. The traditional search requires a perfect match between the sample DNA taken from the crime scene and someone’s DNA from the database. Since DeAngelo had never been convicted of a crime, he had never given a sample to be entered into CODIS so there was no perfect match for the DNA he left at the scene. In contrast, FDS allows law enforcement officers to analyze DNA samples from a crime scene for imperfect matches of family members from within a DNA database. Here is a simplified explanation of the process. Since DNA is inherited, family members will contain more shared genetic markers than non-related individuals do. As such, if law enforcement finds two sufficiently similar matches, they can, with a reasonable degree of probabilistic certainty, conclude that the two individuals are related. So, using FDS, if law enforcement...
