"Junk" DNA assumed a privileged place this summer in the law of criminal procedure.
In Maryland v. King, a majority of the Supreme Court authorized police to take DNA from anyone they arrest, as long as the only part they analyze is the "junk" that doesn't encode instructions for making proteins, and so can't, the Court asserted, reveal "more far-reaching and complex characteristics like genetic traits." The Ninth Circuit later explained the lesson from King that "the government may extract junk DNA... to generate profiles for inclusion in [the national database], because present scientific understanding indicates that junk DNA reveals no sensitive, private genetic or medical information."
The constitutional hang-up on "junk" DNA is incomplete. It's not just that our "scientific understanding" of it is changing. Gene sequencing research that was published last week in the scientific journal Cell suggests that "junk" is capable of controlling important aspects of cell development, by showing how certain white blood cells use non-coding "junk" DNA to regulate the activity of genes in ways that determine their shape and function.
More critical is that when DNA comes from suspects whose identities are unknown to police, they are free to analyze more than the "junk." Say a crime's been committed and you're innocent. You haven't been arrested either. But a few of your skin cells are recovered from the crime scene. This happens more often than you'd think. Your DNA may then be "evaluated more broadly," as Chief Justice Roberts put it during oral arguments in King, not just for identification, but for "all sorts of other stuff."
The federal government is in fact actively pursuing research to expand the scope of that "other stuff." The National Institute of Justice is funding a new technology called DNA phenotyping that seeks to infer physical traits -- like skin, hair, and eye color, even cleft chin, receding hairline, or freckles -- all from the DNA of an unknown suspect. The technology works by comparing a person's DNA with a statistical composite of three-dimensional photographs of people included in a global database who share a similar genetic ancestry.
A primitive version of this technique was already used to catch a serial killer in Baton Rouge. And scientists insist it will soon be developed to the point that it could use a strand of hair to identify an unknown suspect as Chechen, for example, in a case like the Boston Marathon bombings. Four states have forbidden the use of DNA phenotyping in criminal investigations. But it's not as scary as it might sound.
Critics of the forensic technique argue that its adoption would imperil individual privacy and facilitate racial profiling. These objections are important, but they're overstated. What "a person knowingly exposes to the public," the Supreme Court has held, "is not a subject of Fourth Amendment protection" against unreasonable searches and seizures. And statutory safeguards could be afforded for sensitive external traits about whether a suspect has changed genders, for example, or had plastic surgery.
Racial profiling is another concern. That the technology could be used to target minorities at disproportionate rates, however, gives no reason to think that such misuse is probable or any more likely than DNA dragnets or stop-and-question sweeps based on race-based suspect descriptions. The adoption of more precise physical markers in place of notoriously unreliable eyewitness observation would improve arrest accuracy and enhance police legitimacy. The more serious worry is that DNA phenotyping might resurrect discredited conceptions of racial biology.
If the technology works as well as the government is banking it will, however, then replacing race-based suspect designations with the colors and shapes of facial features could, to the contrary, loosen the hold that race has on the way that people think about crime. Today's all-points-bulletin for a "black man" could give way to tomorrow's search for a suspect with dimples, copper complexion, and green eyes.
Wouldn't police just filter these markers into racial terms? Maybe not, if they're trained like clerks at a makeup counter are to trade in racial identifiers for face shapes and color tones. Besides, measures short of prohibition would likely soften whatever risk the adoption of DNA phenotyping would pose to egalitarian norms -- for example, requiring higher burdens for investigatory use, or racial impact assessments of the kind that gained national prominence after the Supreme Court struck down a key provision of the Voting Rights Act.
The next great controversy over forensic DNA won't have anything to do with whether police can test "junk" DNA from people whose identity they already know. It will be about whether police can look "more broadly" at the "other stuff" that genetic information can reveal from people who aren't yet known to them. That our DNA could serve as an eyewitness has powerful implications, beyond individual privacy, for the pervasive role of race in the investigation of crime.