A US government plan to routinely collect DNA data from immigrants in federal custody is sparking concerns among scientists about privacy and discrimination.

The move, announced on 2 October by the Department of Homeland Security, would see DNA profiles of all immigrant detainees stored in an FBI database originally created to help law-enforcement agencies solve violent crimes. The department is still developing regulations that would govern the expanded testing. More than 40,000 people are currently being held in detention centres across the country.

Proponents of the move say the information could help solve crimes, allowing law-enforcement officials to cross-reference the genetic profiles of immigrants with unidentified DNA recovered from crime scenes. But bioethicists say that the efforts will wrongfully target an already vulnerable population.

“To me, this is equivalent of a collection from an entire apartment complex where there’s been a murder or where there might be crime,” says Sara Katsanis, a bioethicist at Northwestern University in Chicago, Illinois, who opposes the government’s plan. “If we treat everyone like they’re a criminal, then that, to me, goes against the principles in the United States.”

It is not clear exactly what data the government will collect, or how, but experts assume that will include the 20 markers that make up the typical DNA profile in the FBI database, the Combined Index Data System (CODIS). These markers are specific short tandem repeats (STR) — repeating regions of DNA that vary in length from person to person.

The STRs used for CODIS are from noncoding regions of the genome and theoretically don’t convey any health information apart from biological sex. The idea is that they are “almost as pure in function as fingerprints”, says Hank Greely, a bioethicist at Stanford University in California.

Breadcrumb trail

But the genetic profiles do provide more information than the fingerprints that the government already collects from all detained immigrants. The STR profiles can indicate whether two people are related and can be used to investigate past or future crimes in which biological fluids were recovered. Research has shown that STR profiles can also be matched to more complete genetic data, such as the profiles used in health research or ancestry databases, which include hundreds of thousands more markers.

In a 2017 study¹ that looked at two sets of genetic data from about 900 genomes, scientists found that they could match STR profiles containing the 13 markers then used in CODIS to more informative profiles, with at least 90% accuracy. The findings suggest that CODIS profiles could be used to identify anonymized genomes from health-research databases or other sources. That same year, CODIS adopted seven additional markers, meaning that such links could be even easier to make.

Access to DNA information could put immigrants at risk of privacy violations and genetic discrimination, says Rori Rohlfs, a statistical geneticist at San Francisco State University in California. In theory, she says, CODIS data are stored securely and used only for identification — but cybersecurity is never guaranteed. If the data were to get out, they could be used to deny a person employment or life insurance, for example.

And because family members share DNA, the government’s plan has implications for immigrants’ relatives — some of whom might be US citizens, the American Civil Liberties Union said in a statement.

The risks posed by DNA collection would increase if, in future, the government decided to use stored samples to run detailed genetic tests. “It’s not totally unreasonable to worry about scope creep and the purposes of these databases changing,” Rohlfs says.

But even the least-informative genetic tests could pose a risk. Being in the CODIS database means that a person has a chance of becoming a suspect for a crime they had nothing to do with. Although CODIS matches are very accurate for high-quality samples, forensic scientists are sometimes forced to work with degraded samples, in which only a fraction of the standard STR markers can be detected. Such low-quality samples come with an increased risk of false-positive matches.

False positives

Individuals whose information is stored in the CODIS database are also exposed to other pitfalls of DNA forensics. These include ‘secondary transfer’ of genetic material. In 2012, a California man named Lukis Anderson was arrested for a murder he didn’t commit. Authorities eventually determined that Anderson’s DNA had hitch-hiked to the hands of the murder victim by way of paramedics who responded to the scene shortly after treating Anderson. Putting more people in criminal databases increases the chance of mistakenly matching an innocent person to a crime.

“If you put a whole population of people in the database and you have very effective but not infallible measures, then that’s going to put that population more at risk for whatever errors do occur,” says Rohlfs.

Above all, the efforts will simply lead to more inequity in law enforcement by subjecting immigrants to further, unmerited scrutiny, says Katsanis.

“We already have a database that is skewed towards African American and Latinx populations,” she says. “It adds to the skewing of the justice system that we will solve crimes committed by African Americans and Latinx people, rather than white people.”