Police increasingly turning to genetic genealogy to crack cold cases

Every few weeks, law enforcement seem to be reporting another cold case solved based on the use of DNA and genetic genealogy, including two high-profile cases in the D.C. area.

The growing popularity of at-home DNA tests offered by companies like 23andMe and Ancestry have helped police build a database to compare crime scene evidence against, which has lead to matches and arrests.

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The commercial DNA testing companies do not share your information with law enforcement, but nearly 1.5 million people have chosen to upload the data received from those tests to two websites that let people discover family connections, Gedmatch and Family Tree DNA. Those websites can be searched by law enforcement, especially if users opt in to those terms.

Parabon, a Northern Virginia company, works with police to make the DNA comparison and provide them with a lead, typically a name which represents a third cousin of the suspect. From there genealogists on Parabon's team use public records to build a family tree and then narrow down the search for the suspect. Those same records can also be used to exclude a suspect. It's possible for the DNA analysis and faimly tree building to yield just one name of a likely suspect.

"The Golden State Killer case was the case that really put genetic genealogy on the map," said Steven Armentrout, CEO of Parabon.

Police agencies have essentially only been using this application of DNA since the suspected Golden State Killer's arrest in April 2018.

Since then, Parabon has helped police solve 88 cases this way.

One of the final steps is police obtaining a DNA sample from the suspect using it to confirm a match to the DNA left at the crime scene.

FILE: This illustration picture shows a saliva collection kit for DNA testing. Between 2015 and 2018, sales of DNA test kits boomed in the United States and allowed websites to build a critical mass of DNA profiles. (ERIC BARADAT/AFP via Getty Images)

"They should never feel comfortable that they've gotten away with what they did," said Christopher Flanagan, a cold case detective with Fairfax County Police.
Flanagan says his unit has worked with Parabon to develop composite images of suspects based on DNA, but is also considering using DNA and genetic genealogy to develop the name of suspect if that seems like the best way to generate new leads.

This process had led to dozens of breaks in cold cases across the country, including at least two in the D.C. region.

In November, police announced the arrest of the accused Potomac River Rapist. Giles Daniel Warrick is accused of murder and violent rape spree in the 1990s. His name was discovered using genetic genealogy.

A similar process led to the conviction of Alexandria nurse Jesse Bjerke. He pleaded guilty to raping a lifeguard in Alexandria in 2016.

Bjerke's DNA match as the suspect was confirmed after police took a discarded straw to test for DNA which they compared to DNA from the victim.

Lawyers for Bjerke argued that police obtained his DNA illegally. The argument did not hold up in court, but under terms of his guilty plea lawyers can challenge it in an appeal.

Parabon says it is working on hundreds of cases using genetic genealogy to help solve cold cases. They are expected to face legal challenges.