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Genetic Linkage

Comparing Adam Lanza’s DNA to Forensic DNA Databases: A Modest Proposal

Is there a genetic signature for violence? It's an old and controversial question. (NHGRI)
In 1729, Jonathan Swift of Gulliver’s Travels fame published a satirical essay called "A Modest Proposal." He suggested that a cure for poverty was for poor people to sell their children to rich people as food.

I’m borrowing Swift’s essay title to bring up another outrageous idea: analyzing forensic DNA databases for a genetic signature of criminality.

Days after the Newtown shootings of December 14, 2012, headlines trumpeted the state medical examiner’s request of University of Connecticut geneticists to examine mass murderer Adam Lanza’s DNA. What exactly that might entail wasn’t announced, but celebrity docs, geneticists, and bloggers weighed in, nearly all agreeing that (1) violent tendencies are due to complex interactions of many genetic and environmental factors and (2) probing Lanza’s DNA and finding anything even suggestive of causing his crime could lead to stigmatization of individuals who share suspect genome regions with him.

Behind the denials of a genetic explanation for criminality lies a history of just such associations.

Past candidates for criminal DNA, listed in many articles last week, include the extra Y chromosome of the 1960s and the monoamine oxidase monoamine oxidase (MOAO) mutation behind a Dutch family of arsonists and rapists, described in 1993. Shortly after, researchers identified a different gene variant that tracked with violence and suicide in Finnish families.

A year ago, criminologists published a study that applied a "delinquency scale" to assess whether such behaviors as painting graffiti, lying to parents, running away, and stealing, were more likely to affect identical twins than fraternal twins, suggesting a genetic component. The headlines that the article in Criminology spawned, with the help of news release hype, were predictable: “Life of crime is in the genes, study claims.”

If an investigation of petty crimes inspires these headlines, the fear of unleashing genetic discrimination from Lanza’s DNA analysis seems justified. Yet it appeared odd to me that several articles deemed any response to the sequencing of the killer’s DNA unlikely, because it would be a sample size of one.

We do, in fact, have sources of criminals’ DNA. And they’re extensive.

A blog from the Council for Responsible Genetics, for example, claims that “Focusing on the results of the study [on Lanza] could also prove problematic since there is (sic) basically no data to compare it to," then quotes a University of Massachusetts Medical School professor saying “we don't have enough of a sample size."

But forensic DNA databases in many countries have been storing the DNA of convicted criminals since the mid-1990s, many killers among them.

The UK led the way in DNA profiling (I wrote the cover story on it for Discover in June 1988), and their National DNA Database now has samples from more than 6 million individuals.

In the US, the Combined DNA Index System (CODIS) has more than 10 million samples. Thailand just signed on to use CODIS on voluntary samples from 100,000 inmates, and 39 other nations already use the system.

CODIS generates a DNA profile for an individual based on 13 sites in the genome that vary in the number of repeats that they harbor. One such “short tandem repeat” (STR), for example, includes the DNA sequence “GATA” present in 5-16 copies on each of a person’s two chromosome 7’s. For that marker alone, 78 combinations are possible. Multiplying the frequencies of the different variant (allele) possibilities in a particular population for all 13 markers generates enough diversity to distinguish individuals.

Within the STR DNA profiles of these millions of convicted individuals may emerge a genetic pattern that’s more common among mass killers like Lanza. Maybe significantly so. If researchers have access to DNA samples, and not just CODIS profiles, they could, theoretically, compare any part of the genome. If there is such a thing as measurable inherited criminality, then as the numbers build in the databases, then associations between DNA patterns and certain behaviors may strengthen, perhaps suggesting a mechanism that can be used in drug discovery or repurposing.

A very large control group would also be necessary to weed out potential false positives, like showing that a disease-causing mutation is found only among patients.

DNA forensic data could and should be de-identified, because the crimes are important, not the names. According to the FBI CODIS factsheet, “If all personally identifiable information is removed, DNA profile information may be accessed by criminal justice agencies for a population statistics database, for identification research and protocol development purposes, or for quality control purposes.“ And informed consent isn’t required of convicts.

Would use of a genetic signature for criminality plunge us into the world of Minority Report, the 2002 Tom Cruise film in which police in a dystopian society arrest people before they’ve committed crimes? I would hope not. But I can imagine a scenario in which a psychiatrist uses such a genetic test for a patient whose background suggests violent tendencies. The patient wouldn’t suffer Tom Cruise’s fate of premature punishment, but perhaps wouldn’t be allowed to purchase a gun.

A powerful argument against the use of forensic DNA databases in crime research is that minorities such as African-Americans are overrepresented in prisons, and findings could be used in a discriminatory manner. This was the reasoning behind the yanking of NIH funding from a conference on “genetic factors in crime” in 1992 at the University of Maryland, with charges of it being a “modern-day version of eugenics” (which is actually timeless).

But times, and technologies, have changed. The 1992 objection to even investigating genetic factors in crime predates the DNA Identification Act of 1994 that led to forensic DNA testing by 1998 – now done in all 50 states. And consider the most notorious recent killing sprees. The perpetrator of the worst attack, at Virginia Tech in 2007, was Asian, Seung-Hui Cho. The Columbine killers Eric Harris and Dylan Klebold were white, as is James Holmes of the midnight movie massacre in Aurora, CO in 2012. And the blurry, terrifying lone image of Adam Lanza is stark white.

I’m playing Devil’s advocate here. I agree with other geneticists that looking for clues to the Newtown tragedy in DNA could do more harm than good. I also agree that environmental influences on behavior and personality are as important if not more so than inherited factors. But at the same time, I can’t help thinking of those forensic DNA databases and the clues to violent behavior that they may hold, anonymously searchable by crime. And we now have the technology to derive much more information than we did when the technology was limited to selected repeats – we can sequence genomes. That’s a lot of information.

Uses of forensic DNA technology are already eclectic enough to embrace investigation of a criminal tendency profile.

STR typing has been used to identify disaster victims, to reunite Holocaust victims with their families, and to identify kidnapped children. And DNA profiling of footballs from Super Bowl games protects a vulnerable public against sports memorabilia fraud.

So despite lingering apprehension from the history of eugenics in the US in the early twentieth century, the threat of stigmatization, and growing acceptance of genetic determinism as genetic testing and genomes/exome sequencing become more widespread, I’m going to make that modest proposal.

I think that the DNA forensic databases may be important sources of information on the role, if any, of genetics in predisposition to violent behavior.

We have the data. Why not take a look? It’ll keep bioethicists busy for years to come – and might prevent a crime.

This blog first appeared at PLOS blogs.
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