The Gilded Margin

Brain Day|The Gilded Margin

There are few things quite as personal as your family tree.

It is a collection of names, dates, photographs, stories, questionable family legends, and at least one relative everyone insists was a very interesting character. It can also be a surprisingly powerful investigative tool.

Forensic genetic genealogy takes the science of DNA analysis and combines it with traditional genealogical research to help investigators generate leads in certain unsolved cases.

You may have heard about it through high-profile cases, documentaries, or the growing popularity of consumer DNA testing. The basic idea sounds simple enough: use DNA to identify biological relatives, build a family tree, and work toward identifying an unknown person.

The actual process is considerably more involved. Because, naturally, science refuses to let anything be as simple as the television version.

Not the same DNA search you may be imagining

Most people are familiar with traditional forensic DNA profiling, particularly the type of DNA profiles used in the Combined DNA Index System, better known as CODIS.

Forensic genetic genealogy uses a different approach.

Traditional forensic DNA profiles commonly examine short tandem repeats, or STRs. Forensic genetic genealogy uses a much larger set of genetic markers called single nucleotide polymorphisms, or SNPs.

The Department of Justice describes forensic genetic genealogy as a process that can examine hundreds of thousands of SNPs across the genome. These markers can help identify shared stretches of DNA between an unknown sample and people who have voluntarily submitted genetic information to participating genealogy databases or services.

The more DNA two people share, the more closely related they may be. That information can help researchers identify possible familial relationships.

And that is where genealogy comes in.

Building a family tree from genetic clues

Imagine investigators have an unknown DNA sample from a case. Traditional database searches have not produced an identification, and the case meets the criteria for considering forensic genetic genealogy.

A suitable sample may be sent to a specialized laboratory for SNP-based analysis. The resulting profile can then be searched in an appropriate genetic genealogy database under the applicable rules and permissions.

A potential genetic relative may appear.

That match does not identify the unknown person. It gives investigators a possible family connection.

Genealogical research can then help build out family relationships, examine records, compare timelines, and narrow the possibilities. Researchers may use public records, historical documents, family trees, and other legitimate sources to understand how the potential relatives could be connected.

The work is often less dramatic than a television montage of photographs and red string. It can involve a great deal of careful research, checking, and eliminating possibilities.

The goal is to develop an investigative lead that can be evaluated through additional evidence.

A lead is not an identification

This is the part I really want to emphasize.

A genetic association generated through a genealogy search is not, by itself, proof that a particular person committed a crime. It is not an automatic identification, and it should not be treated as one.

The Department of Justice’s interim policy specifically states that investigators should not arrest a suspect solely on the basis of a genetic association generated through a genealogy service. Traditional genealogy research and additional investigative work are necessary to determine the nature of the relationship.

If investigators identify a person of interest, they must still pursue appropriate corroboration. Depending on the circumstances, that may include obtaining a known reference sample and conducting conventional forensic DNA comparison, along with other investigative steps.

In other words, the family tree can point investigators toward a door. It does not tell them what is on the other side.

The privacy question is part of the conversation

This technology also raises questions that deserve more than a passing mention.

When someone submits DNA to a consumer genealogy service, they may be thinking about ancestry, family connections, or discovering relatives they never knew existed. They may not be thinking about how their genetic information could intersect with a criminal investigation.

The DOJ policy addresses privacy and civil-liberties considerations, including when the technique may be used, the databases involved, and the handling of genetic information.

The details matter. Database policies differ, and users should understand the permissions and privacy settings associated with the services they choose. A person’s decision to participate in a genealogy service can also have implications for biological relatives who never submitted a sample themselves.

That is one reason forensic genetic genealogy should not be treated as a magic search button. It is a specialized investigative technique with limitations, rules, and responsibilities.

The science is impressive. The responsibility is even more important.

Forensic genetic genealogy has helped investigators pursue leads in cases that might otherwise remain unresolved. It can also assist in identifying unknown human remains, giving families answers after years of uncertainty.

But the value of the technique depends on how carefully it is used.

The science can generate a lead. Genealogy can help interpret a possible relationship. Investigators must do the work to establish what that relationship means. And any eventual identification must be supported by appropriate evidence.

That is a lot of work behind what often gets reduced to a headline that says DNA solved the case.

The more accurate version is that DNA helped open a new investigative path. People still had to follow it, verify it, and establish the facts.

Which is a little less cinematic, perhaps, but considerably more important.

A family tree may begin with names and dates. In the right circumstances, it can also become one piece of a much larger effort to answer questions that have waited years for an answer.