Case Study: Targeted Swabbing When Genealogy Trees Aren’t Enough?

The breakthroughs of forensic genealogy have been positioned as a new application of advanced DNA analysis atop time-honored tradition of constructing family trees through public records like obituaries and birth and death records.

But what happens when the family tree reaches a dead end—and the branches don’t fully connect?

In at least one investigation, you start swabbing other parts of the family tree—adding more data to the genealogy inquiry.

The revelation of active DNA searching through the addition of more samples to triangulate an unknown person is identified in a new paper by one of the forensic genealogy providers, the Virginia-based Parabon NanoLabs, published in the journal Forensic Science International.

“As this case study shows, if family members of the matches are willing to cooperate, targeted kinship testing can quickly include or exclude various branches of the family tree and thus arrive at a small number of included individuals,” write the authors, Ellen Greytak, Steve Armentrout and CeCe Moore.

Like many other legal aspects of forensic genealogy, the legal implications of such “targeted kinship testing” have not yet been tested by defense attorneys in court. 

In the new academic paper, Parabon lays out some of the challenges and successes in the year since the much-vaunted capture of the suspected Golden State Killer, Joseph James DeAngelo, a breakthrough made possible by genealogist Barbara Rae-Venter.

The company authors list 28 of the high-profile investigatory breakthroughs, done by various genealogists. The company also cites that 80 percent of Parabon’s roughly 250 law enforcement cases resulted in a match of third cousin or closer, a roughly 60-centiMorgan (cM) threshold.

But in their paper’s final case study, from which almost all identifying details are withheld, Parabon points to a different way to get at their person of interest: going out and getting more buccal swabs from people on family trees.

The roughly 40-year-old homicide cold case had a DNA profile of an unknown suspected perpetrator, which was run through GEDmatch. That yielded top two matches in the sixth to eighth relative degree, translating to approximately 100 cM.

The family tree reconstruction went back to great-great-grandparents—but there was no intersection, and the identity could not be triangulated further, according to the paper.

Parabon recommended further research—and “targeted kinship testing.”

So the cops went out and swabbed two people to clarify the family tree. The voluntary swab was from a cousin on the first match’s paternal side. The second was a voluntary buccal swab from a cousin on that same person’s maternal side, which was “predicted with 94.2 percent confidence to be a 3rd degree relative (first cousin or genetic equivalent) to the Subject.”

Further family trees for the spouses of each of the kinship tester’s maternal aunts went back further to the great-great-great-grandparents, according to the paper. Only then did they find one uncle’s wife who was determined to be a distant cousin to the one of the purported killer’s more distant matches. That narrowed down to a single couple—and their male children. Those children were also the “right age at the time of the crime,” and lived nearby at the time.

The Parabon paper also argues for the legality of the use of GEDmatch, stating it is not a privacy violation since the database is voluntary and not legally required.

The three Parabon authors further distance it from familial searching, or FS, which they contend is “legally required” since such DNA-relation connections are made through government databases of convicted offenders. But FS has not appeared to require further testing of volunteers to provide focused investigative leads to full siblings, or parent/child relationships.

Genealogy breakthroughs continue, and they continue to grab headlines. In the meantime, Rae-Venter, the woman credited with starting the high-profile use of the technique, was named to the Time Magazine “100 Most Influential” list for 2019.

The Washington Post recently reported that the head of the Nationals Consumers League was calling for regulation of at-home DNA testing kits and the “Wild West” of how they are being used in forensic science.

By Forensic Magazine.

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