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Professor Jennifer Mnookin Publishes Op-Ed in the Los Angeles Time

Professor Mnookin Discusses Issues Facing Partial DNA Matches in Criminal Investigations


April 5, 2007 -- IF YOU'RE CONVICTED of a felony (or in some states a misdemeanor), your DNA goes into a database. That information primarily helps in the pursuit of repeat offenders. But some people want to extend the reach of that data to find people who are only a partial match. It's a particularly personal form of a law enforcement fishing expedition.

The technique is called "familial searching," and it targets not only the convicted but their relatives as well.

Sometimes, when an investigator tries to match a crime scene sample to the several million profiles in, say, the FBI's database, no exact match turns up. But there might be someone whose DNA profile is unusually similar. If the partial match is sufficiently close, or if some of the genetic markers in the sample are sufficiently rare, it could mean that the crime scene sample was left by a close genetic relative of the person who is included in the DNA database. Thus the familial search casts suspicion not on the convicted criminal in the database but on that person's siblings, parents or children.

Should forensic scientists reveal partial matches to police and prosecutors? Should officials be able to use this DNA as the basis for investigating relatives? Is this a lead that any investigator would be crazy to ignore, or is it an encroachment on civil liberties?

The difficulty is that it is both. While mining the DNA database for clues is certainly tempting, it is a temptation we should resist. Fairness and privacy concerns require it.

Although Britain has been using familial searches for several years, it's just arriving in the United States. Until recently, the FBI refused to allow states to reveal partial matches in its database to other investigatory agencies, but it's beginning to soften that stance. Many prosecutors, including those in California, are lobbying hard to be able to use the technique, and a 2006 article in Science argued that the use of such kinship analysis could increase the number of cases that were solved by up to 40%.

It's easy to see the arguments for using familial search techniques. If we forgo partial matches, violent criminals may remain at large. There are some powerful anecdotal examples of how familial searching has led police to suspects. And we use partial information all the time in other settings. If someone looks at suspects in a photo spread, for example, and says, "It's not any of those people, but the perpetrator looked a lot like No. 3," any competent investigator would think to ask if No. 3 had a brother.

Yet we should resist the impulse to engage in familial searching. Put plainly, it is discriminatory. If I have the bad luck to have a close relative who has been convicted of a violent crime, authorities could find me using familial search techniques. If my neighbor, who has the good fortune to lack felonious relatives, left a biological sample at a crime scene, the DNA database would not offer any information that could lead to her.

When DNA databases were first put into use, there was much debate about whether they were an impermissible invasion of people's privacy. The argument that generally won out was that convicted criminals gave up some privacy rights. But those people who just happen to be related to criminals have not given up their privacy rights as a consequence of their actions. To use a search technique that targets them simply because of who their relatives are is simply not fair.

This concern is exacerbated because African Americans and Latinos make up an outsized portion of the DNA database compared with their proportion in the population at large. This means that African Americans and Latinos not in the database would be disproportionately available to familial searching. The same point could be made for the poor and working-class populations compared with those who are wealthier.

While we might not be sympathetic to the claim of a privacy violation made by a guilty person caught by familial search techniques, we ought to care that these procedures disproportionately affect the underprivileged.

But apart from these disparate racial and economic factors, it is not right to have an investigative technique that targets not just convicted criminals but also their relatives while leaving the rest of us immune. Moreover, the broader the parameters for partial match searches, the more likely false positives become.

Those who are not troubled by familial searching ought to have the courage of their convictions and take their implicit logic one step further. If it is ethically and legally acceptable to use DNA search techniques on people without prior convictions, then why not have a national database that includes everyone? The onus ought to be on the advocates of familial search techniques to justify why they should be allowed.

My point is not to argue that we should (or shouldn't) have a universal database. But as a matter of fairness, it ought to be all or nothing. The misfortune of having a criminal in the family tree ought not to be what determines whether a DNA search can find you.

By Jennifer Mnookin, JENNIFER MNOOKIN is a professor at UCLA's School of Law.