Genealogy and the Golden State Killer

SQ WINTER INSIDER 2020

Genealogy and the Golden State Killer

Text & Illustration by VARSHA RAJESH

A hundred burglarized homes. Children quivering with fear behind closet doors. Violently murdered couples. All the work of one man–California’s most prolific murderer, the Golden State Killer. From 1974 to 1986, police departments along the west coast struggled to keep up with his crimes. The Golden State Killer left no fingerprints and always wore a mask, leaving his surviving victims incapable of identifying him. But he left one crucial piece of evidence: DNA.

In 2001, after the development of modern genetic testing, DNA evidence across different crime scenes was used to connect all the crimes to one person. But, the DNA did not match any known person in federal DNA databases. So, how did we finally catch him?

The story begins not in a police station, but with the field of genealogy. Genealogy has been used to track family histories for centuries. Recent developments in sequencing technology have allowed researchers to use genetic variation between humans and chromosomal recombination, in addition to family records, to establish ancestry.

What is recombination? In humans, sex cells are produced when diploid cells undergo meiosis. During this process, homologous chromosomes line up, break off, and exchange genetic material, causing increased genetic diversity in the daughter cells. Genes around the breakage point on a chromosome become separated and are no longer “linked.” A stretch of genes in a person’s chromosome becomes greatly unlinked by the time their grandchild inherits them, because of the numerous rounds of recombination that occur with every generation.

Sequencing an entire section of genes is expensive and time-consuming. As a solution, direct-to-consumer (DTC) companies like AncestryDNA and 23&Me sequence single nucleotide polymorphisms (SNPs), which are one-nucleotide variations in the genome. Two people sharing a long stretch of SNPs are closely related, while two people sharing little to no SNPs are distantly related.

In 2010, the public database GEDmatch was created to help people find their relatives. Information purchased from DTC companies can be uploaded as profiles to GEDmatch, which then uses its own algorithms to establish relationships between users. When Detective Paul Holes uploaded the Golden State Killer’s sequenced DNA from the Ventura County rape kit to GEDmatch, more than a hundred profiles came up as relatives. The team took almost four months to construct numerous family trees that narrowed down the pool of suspects to two, one of which was Joseph James DeAngelo, Jr.

Suspicious of DeAngelo, a 73 year-old retired cop living in Sacramento County, police discreetly collected his DNA samples from his car doors while conducting surveillance. When tested, this DNA matched that of the crime scene, and the Golden State Killer was finally unmasked.

Since then, more than 50 cases have been solved with the help of forensic genealogy, according to NBC. However, the field is expanding at such a rate that investigators, genealogists, and crime labs are operating with minimal restrictions on issues like privacy. After consumers voiced concerns about law enforcement having access to the GEDmatch database and accusing relatives, the company changed their policy to require users to “opt-in” if they wanted their information to appear in searches conducted by law enforcement. However, The Atlantic reports that only 163,000 users of the 1.3 million have opted in, severely restricting the ability of law enforcement to construct complete family trees.

Another privacy issue is that anyone can upload DNA with the intention of constructing a suspect pool, and these profiles are extremely hard to track and remove because they are not flagged as law enforcement. Users who opted-out of sharing information with law enforcement could still be considered in these searches.

In 2018, DeAngelo was charged with 13 counts of murder, and his preliminary hearing is set for this year. He did not enter a plea. While his trial is still ongoing, forensic genealogical methods have yet to be used as official evidence; in every case so far, offenders have either died prior to the conviction or pled guilty. But the presentation of this technology in a courtroom is inevitable. Solving a 30 year cold case brings peace of mind to countless victims and their families, but at the cost of users who unwittingly upload information that could implicate their relatives. Which one is more important? Currently, our privacy is protected, but a verdict could easily override the status quo.

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