The Case for a Universal DNA Database: Think of the Crimes We’d Solve

Eric Posner weighs in.
March 5 2013 12:04 PM

The Mother of DNA Databases

If we really cared about protecting the innocent, we’d collect samples from everyone—not just the convicted.

Forensic worker Rayo Del Carmen Ochoa examines DNA samples
Forensic worker Rayo Del Carmen Ochoa examines DNA samples

Photo by Henry Romero/Reuters

Last Tuesday the Supreme Court heard a debate about whether police should be able to swab the cheek of a person they have arrested, in order to obtain genetic information from him. The man arrested, Alonzo King, got in trouble for brandishing a shotgun at some people, but after analyzing his DNA sample, police discovered that his profile matched DNA evidence taken from a rape victim. King was subsequently convicted of the rape. And then the Maryland Court of Appeals held that the acquisition of the DNA sample was an unreasonable search that violated the Fourth Amendment of the U.S. Constitution.

The case turns on the distinction between merely arrested people (who are presumptively innocent) and convicted people (who are presumptively guilty). If the police had taken the sample from King’s cheek after he had been convicted of a crime, he would clearly have had no constitutional claim. Earlier cases have established that convicted criminals have limited privacy rights and taking DNA samples from them doesn’t come close to violating them. But King’s DNA was taken when he’d been arrested and not yet convicted.

Maryland argues that arrestees also have limited privacy rights. The police must have probable cause to arrest someone, but once they do, they can search his person, photograph him, and fingerprint him. He can even be strip-searched. A person suspected of drunken driving can be required to take a Breathalyzer or jabbed with a syringe. Compared with these indignities, the intrusion in privacy from the cheek-swab is essentially nil. The procedure itself takes only a moment, and the portion of the DNA molecule that is analyzed can reveal nothing about the person other than whether he was present at a crime scene from which the matching DNA was taken. It does not reveal the identities of his parents, or ethnic heritage, or genetic disorders, or the structure of his soul.

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King argues (as do the ACLU and two law professors writing in Slate, Brandon Garrett and Erin Murphy) that the government’s interest in the information generated by the cheek-swab is minimal. DNA information collected from crime scenes and convicted criminals account for nearly all the matches that help solve crimes. As Garrett and Murphy note, King had six prior convictions, and most people who are arrested have prior convictions, given the huge amount of recidivism among criminals, so you can get most of the information you need even if you are limited to taking DNA samples from convicted criminals. But Garrett and Murphy do not show that the additional information from expanding the net to arrestees is zero; and as more DNA samples become available for analysis, police will be able to solve more crimes.

The Fourth Amendment requires a balancing of the privacy interests of individuals and the criminal-justice interests of the states. Thus, this seems like a case in which you put a feather on each side of the scale, and it tips in neither direction. So each side gilds the feather with familiar exaggerations. King’s defenders warn that the state could demand DNA information from people who have been stopped for running stop signs or who have applied for drivers’ licenses. Maybe this information will then get out, or be used by the government to identify people with criminal dispositions and convict them before they commit crimes, like in Philip Dick’s story, The Minority Report. The state, on the other hand, paints a rosy picture of the future of DNA analysis, going perhaps beyond what is scientifically feasible.

A court must decide the case before it, not all future cases that may arise as a result of a rapidly changing technology. Whatever value DNA information may have for identifying embarrassing secrets or the propensity to future crime, the system before the court uses DNA for the purpose of matching criminals to crimes—and none other. And while government officials could conceivably break the law and sell DNA samples to insurance companies or telemarketers, or trumpet private information to the press, they can do that with all the other information they possess—from tax returns to health records. Laws deter this behavior. If we are to deprive the police of useful but dangerous tools merely because they could be misused, we should start by taking away their guns.

Indeed, the idea that the police would use DNA evidence of a person’s criminal propensity to lock her up before she commits crimes is farfetched at best. Scientists currently do not believe that a person’s DNA provides useful information as to whether he will commit a crime in the future—the intervening environmental factors, like where and how a child grows up, probably swamp genetic influences. And even if it did, it is no more plausible that society would allow police to lock up people with “bad” DNA than that it would allow police to lock up adults who exhibited aggressive personalities as children (according to this paper, a pretty good predictor of adult criminality). Genes or no, the rule is that you must commit a crime before being convicted of it.

King’s defenders make another argument. Under current law, when police arrest people, they can only search for weapons and evidence that might be destroyed—not for information that could be used to fish out new crimes. Thus, if you are arrested for drunken driving, the police can’t search your home in the hope of finding evidence of tax evasion or drug possession. At the Supreme Court argument Tuesday, Justice Kagan suggested that this rule means that police cannot cheek-swab people arrested for one crime in the hope that information about some other crime will be discovered. But police also can’t search people’s houses for evidence of different crimes after convicting them of drunken driving. The real justification for gathering DNA of convicts is that it gives police useful information without requiring a serious intrusion—that is why we draw the line at searching their houses. This logic suggests that arrestees should be required to submit to DNA tests—and indeed that the rest of us should as well.

The Bureau of Justice Statistics estimates that 203,830 rapes took place in the United States in 2008. Most rapists are not caught and convicted. DNA testing provides a uniquely valuable approach to this difficult problem. With a minimal privacy intrusion, it can provide accurate evidence that leads to convictions. If we really care about rights, we should mandate DNA testing, and not only of arrestees, but of everyone. A universal DNA database would greatly increase the number of convictions—vindicating the rights of rape victims and protecting others from serial rapists. It would also, of course, help police solve other crimes in which criminals leave behind hair, blood, flakes of skin, and so on. Such a database would greatly reduce the incidence of false convictions, thus protecting the rights of innocent people who are wrongly accused. And a higher hit rate would cause police to spend more resources collecting DNA evidence at crime scenes, giving them more ammunition for solving cold cases—just because the higher payoff in terms of convictions would justify the higher costs.

Yet dinosaurs like the ACLU stand in the way of such sensible reforms, because of their customary focus on the rights of criminal suspects and defendants at the time of arrest and trial. The ACLU’s own DNA prevents it from seeing that superior investigative techniques will do more to protect innocent people than an extra right or two at the stage of arrest. The Supreme Court will likely disagree, and rightly so.

Eric Posner, a professor at the University of Chicago Law School, is author of The Twilight of International Human Rights Law. Follow him on Twitter.

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