The methods used to investigate crime have evolved considerably over time… fingerprint analysis dates back to the 1880s, and the roots of forensic toxicology go all the way back to the first century, but most think of DNA evidence as the most effective tool in the investigator’s tool chest.
The use of DNA evidence is a fairly recent development in the world of criminal investigation, having only become practical in the 1990s, and despite its reputation as ironclad evidence, DNA has its shortcomings and law enforcement has continually pressed to advance investigative techniques even further. With the recent development of genealogical DNA analysis, they may have done just that.
What’s the difference between DNA evidence and Genealogical DNA Analysis?
In a criminal investigation, forensic investigators attempt to preserve and collect any DNA evidence that may have been left at the scene by the perpetrator. Law enforcement then compares the DNA profile generated by a forensic investigator to a database known as CODIS or, the Combined Index DNA System.
When the DNA Profile matches someone already in the system, law enforcement has a suspect to investigate, and they go about the business of building a case. If the suspect identified by DNA can be corroborated by other factors–the suspect lived in the neighborhood, matched an eyewitness description, or was found in possession of other incriminating evidence–the case is made.
The CODIS database contains DNA profiles from a lot of people–those who’ve been previously arrested, served in the military, etc… and although it is a huge database, it’s far from comprehensive. There are simply a lot of perpetrators who have never had their DNA sampled, so when investigators develop a DNA profile based on evidence left at a crime scene, they sometimes get zero matches back from CODIS and the DNA evidence becomes useless, because it doesn’t match anybody in the database. That’s where genealogical DNA analysis has proven to be a huge leap forward.
Genealogical DNA Analysis
Law enforcement’s most powerful tool owes its existence to the family tree and modern genealogy websites. As of this writing, more than 26 million people have taken an at-home DNA test and uploaded the results to one of the four major consumer genetics testing companies. The idea is to connect their DNA profile with others to discover family relationships and build a family tree. It’s a process that can be done much more quickly than the old method of tracking down birth, marriage, and death certificates.
It’s those public DNA databases that make genealogical DNA analysis possible, and the process usually consists of two primary steps: DNA phenotyping and genealogical matching.
DNA phenotyping involves developing a physical description of the suspect based on the physical characteristics encoded in DNA. The human genome was mapped in April of 2003, and in the time since, science has been able to develop techniques to “read” the information within… based on a DNA profile, we can know things about the suspected donor, like gender, hair color and eye color, for instance. Based on DNA phenotyping, law enforcement can generate a general physical description of the suspect they’re looking for.
Genealogical Matching
Once they have a description of a potential suspect, the forensics lab uploads a sample of the suspect’s DNA to a public ancestry database in search of a genealogical match. When a match is made, investigators then proceed with the process of building a family tree based on the match until they find a person who could be the perpetrator.
The process can be very complex.
Imagine this: a person in New York, David Jones, uploads his DNA to an ancestry site to learn more about his family history. Later, a detective uploads DNA from a potential suspect in a California crime and gets a genealogical match to the family tree of the David Jones in New York. The California suspect and David Jones in New York share a common ancestor. For the sake of simplicity, let’s keep the relationship very recent — the California suspect is related to David Jones through a common ancestor a couple generations ago… his great grandfather, Henry Jones.
The detective must then go through the process of building out the family tree starting with the common ancestor… to determine which descendant of Henry Jones is responsible for the crime he’s investigating. The analysis might be something like… Henry Jones had two sons, and those two sons had 7 children between them, and so on. Investigators build the family tree until they find a family line with someone who could potentially be the suspect–a descendant of Henry Jones who matches the description developed through phenotyping, lived in California at the right time, was approximately the right age to have committed the crime, and so on.
The final step to secure an arrest involves recovering a DNA sample from the suspect identified through phenotyping and genealogical analysis, most commonly achieved through surveillance. Investigators would stake out the suspect (a descendant of Henry Jones)–and wait until he or she discards something with their DNA on it–a straw, a cigarette butt, or a coffee cup, for instance. The DNA from the discarded item is tested, and if it matches the DNA recovered from the crime scene, the perpetrator has been identified and an arrest soon follows.
The process was first used successfully to identify and arrest the Golden State Killer in northern California in 2018. The process is not without its challenges, however, particularly with very old cold cases. In situations where the crimes themselves happened decades ago, the perpetrator is likely dead, making it very difficult to retrieve a DNA sample for matching purposes.
The case of the Zodiac Killer is one example. With crimes that took place between 1963 and 1970, the Zodiac is likely (but not certainly) dead, and left no DNA at his crime scenes. Investigators are undaunted, however, and in 2018, attempts were made to recover DNA from the stamps on letters the Zodiac sent to the media. If a DNA profile can be developed, authorities may be able to use genealogical DNA analysis to arrest the Zodiac if the perpetrator is still alive, or at least name him if he isn’t. When and if that happens, you can bet it will be big news.
The Results So Far
In the year after the arrest of the Golden State Killer, a single lab, Parabon Nanolabs, joined law enforcement and a genetic genealogist in investigating 200 cold cases through Genealogical DNA Analysis and the effort resulted in 55 more arrests nationwide. That is a staggering statistic, considering the majority of the cases were long cold with little hope for resolution.
The technology is still in its infancy, and you can bet it will become more effective as investigators hone their technique. It stands to be the most important development in criminal investigation since the advent of DNA as an investigative tool.
Concerns Over Legality
Despite the success of Genetic Genealogy, questions about privacy have been raised, and law enforcement faces a new challenge. One of the public DNA databases the authorities use for Genealogical DNA matching, GEDmatch, recently changed their terms of service so users must opt-in to allow law enforcement to use their DNA in investigations.
When I first heard about it, I asked myself, “Why would anyone object to law enforcement having access to a DNA database for the purposes of solving a crime?” The answer is complicated.
Some people are pre-disposed to distrust governmental agencies like law enforcement, and others who’ve led a life full of questionable behavior have usually had frequent run-ins with the authorities which have left them with an anti-law bias. Those communities are usually the minority, but in the internet era, minority voices are amplified. Perhaps the most vocal objection to law enforcement use of genealogical investigative methods is rooted in privacy.
Take the example I gave you earlier… David Jones in New York uploads his DNA, law enforcement uses the profile to discover a killer is related to his great grandfather Henry Jones, and maps out the family tree identifying every descendant in the family until they find their perpetrator. The privacy concern enters when you consider David Jones, who had nothing to do with the crime, effectively allowed law enforcement permission to analyze the DNA of everyone in his family, potentially going back centuries, without their consent.
Genealogists have also objected due to the divisive nature of the conversation, seeing it as a distraction to the history and family-centric nature of genealogy.
In my personal opinion, as long as gDNA is used for catching murderers and rapists, particularly those who still walk free, never having faced justice, I don’t see any reason to object. It’s when this kind of investigation begins to compromise a person’s privacy that we see a need for strict oversight.
The databases law enforcement presently uses are open-source, which means anyone can copy the information in them… employers and health insurance compa nies, for example. If those entities were to determine a person is pre-disposed to certain conditions… schizophrenia for an employer, or cancer for a health insurer, it may affect a person’s ability to find a job or get insurance coverage. The possibilities are frightening, and the discussion is only just getting started.
Even so, my personal recommendation is, as a person with an interest in true crime, if you have your DNA data already uploaded to a commercial database like Ancestry.com, I would urge you to download your raw data file and upload it to a database like GEDmatch or Family Tree DNA and opt-in to allow law enforcement use, because this is, in my opinion, one of the circumstances where the needs of the many outweigh the needs of the few.
We’ll be discussing a lot of these cases in the near future, so check back for more.
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[music] Very Low Note, Half Mystery, Rising Game,, Interloper, and Cryptic Sorrow by Kevin MacLeod, Incompetech.com. Creative Commons License via FilmMusic.io
[feature photo] Public domain, Library of Congress
