Forensic genetic genealogy (FGG), also called investigative genetic genealogy, combines DNA analysis, conventional genealogy, traditional law enforcement investigation, and direct-to-consumer DNA testing services. It gained prominence in 2018 when it led to the arrest of Joseph James DeAngelo Jr., the so-called Golden State Killer, for 13 murders and kidnappings committed in the 1970s and 1980s.
Since then, it’s been employed in hundreds of cases to solve crimes, exonerate the innocent, and identify unidentified remains. In 2019 alone it helped to:
- exonerate Christopher Tapp, wrongly convicted of murder, by identifying a suspect that matched the crime scene DNA,
- identify a suspect in the 1971 strangulation of Rita Curran, Vermont’s oldest cold-case murder, and
- identify the remains of Joseph Henry Loveless, murdered in 1916 and whose remains were recovered from a remote cave in eastern Idaho in 1979 and 1991.
As its use by law enforcement has increased, federal and state authorities, as well as consumer DNA testing services themselves, have started to develop regulations to control the process.
DNA Databases Help to Identify Individuals and Their Relatives
Genetically, all human beings are 99.9 percent identical (identical twins are 100 percent identical). The remaining 0.1 percent both defines our relative difference and reveals our shared lineages. It can reveal information about a person’s identity, genealogy, and certain physical characteristics such as height and hair color.
To greatly simplify the science, DNA analysis consists of comparing specific locations (markers) on DNA in a sample to comparable markers in a database. An identification search results in a probability that the target sample matches a record in the database. A familial search results in a percentage of similarity indicating a common genetic lineage, with greater similarity indicating a closer relative.
The Combined DNA Index System (CODIS) of the Federal Bureau of Investigation (FBI), developed in the 1990s, initially included 13 markers (expanded to 20 since 2017). These markers were selected because they have a wide range of variation and therefore are useful to identify a match for a target record.
Although not designed for it, the CODIS markers can be used for familial searching. These searches generate a ranked list of potential matches for further investigation. The results contain false positives, and a true relative match may not be the top-ranked entry. Most notably, familial DNA testing was used by Los Angeles police in 2010 to find the serial murderer known as the Grim Sleeper (Lonnie David Franklin Jr.). He was identified through his son, who had been arrested for felony weapons possession, and an investigation that led to the collection of his DNA from a discarded pizza crust.
FBI policy prohibits using its CODIS database with the intent of uncovering a familial match. However, many states allow such searches of their state-level DNA databases, including Arkansas, California, Colorado, Florida, Michigan, Texas, Utah, Virginia, Wisconsin, and Wyoming. In contrast, Maryland and the District of Columbia specifically prohibit familial searching because of concerns that such searches would target people of color, who are disproportionately represented in their databases.
While familial searching works with CODIS, those markers are designed to identify individuals. Genealogical DNA testing, on the other hand, involves using different technologies and examining a greater portion of the DNA. Because of differences in the testing, law enforcement usually outsources DNA sample processing. The outside labs will commonly also upload the generated genetic profiles to consumer genetic services and investigate any detected familial relationships through traditional genealogical methods.