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April 8, 2007

Near-miss DNA Searching

"Familial searching" is back in the news.  60 Minutes had a segment on it last week called "A Not So Perfect Match: How Near-DNA Matches Can Incriminate Relatives Of Criminals," and the LA Times ran an editorial by UCLA Professor Jennifer Mnookin entitled "The Problem with Expanding DNA Searches: They Could Locate Not Just Convicted Criminals But Also Relatives -- Violating Privacy."

The phrase "familial searching" is slightly misleading. As Mnookin notes, when a DNA sample from a crime scene is almost -- but not quite -- a match to a particular individual in the convicted-offender database, it could well come from a full sibling or a parent or child. As one moves farther out on the family tree, however, it is difficult to distinguish relatives from unrelated individuals with the DNA types listed in the database.

Although one cannot expect too much from short editorials and TV clips, it may be worth noting and commenting on some of the arguments against near-miss searching floated in these media. The major argument offered on the 60 Minutes show was that looking for leads to relatives is "genetic surveillance." Of course, this is more of a slogan than an argument. Calling the practice "genetic" or "surveillance" does not make it wrong. People would prefer not to come to the attention of the authorities, but what is the underlying right that following these leads violates? Or is the argument not about rights, but policy? Is the unarticulated premise that the police should not have a way of tracking the whereabouts of large numbers of people who are not (yet) known to have done anything wrong? Perhaps, but don't people become suspects for all kinds of reasons beyond their control all the time?

Professor Mnookin formulates the point somewhat differently when she writes that “[p]ut 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.” The “discrimination” here is that people whose parents, children, or siblings are convicted criminals can be caught. But why is this under-inclusiveness such a serious concern? By this logic, wouldn't it be equally discriminatory to seek or follow up on leads by interrogating friends of a criminal? To paraphrase the editorial, “If I have the bad luck to have a friend who is willing to talk to the police, authorities could find me using interrogation techniques. If my neighbor, who has the good fortune to lack loose-lipped friends, committed the same crime, the interrogation would not offer any information that could lead to her.” “Discrimination” that arises from “bad luck” is not generally a concern. Something else must be doing the work here.

Another less-than-obvious claim cast in terms of "discrimination" or "fairness" is that “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.” But it is not apparent that there is any fundamental “privacy right” to be free from becoming the target of an investigation because of one’s associations with individuals who come to the attention of the police. Suppose that I commit a crime all by myself but I have a nosy neighbor who shadowed me. He gets caught committing a totally unrelated crime, and he bargains for a lower sentence by offering to rat on me. Would we say that “those people like me, who just happen to be living next to nosy 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 neighbors are is simply not fair.”?

A more troubling point is that near-miss searching will have a disparate racial and economic impact because racial minorities and less affluent individuals are overrepresented among convicted offenders. Is the disparate impact is acceptable for the convicts but not for their closest relatives? Mnookin points out that in upholding the constitutionality of convicted-offender databases, courts have suggested that offenders lose privacy rights by virtue of their offenses. I am skeptical of this “forfeiture of rights” argument as the ground for upholding convicted-offender databases, but it is a common intuition, and many courts have relied on it to overcome the Fourth Amendment claims of convicted offenders. Notice, however, that the right be free from bodily invasion asserted in those cases has no application to near-miss searching. Under current Fourth Amendment doctrine, no "search" occurs in looking at validly obtained DNA profiles to determine if there are any near matches. That said, the disparate-impact concern remains, at least as a policy matter. The inequity exists with or without near-miss searching, but more people are affected if near-miss searching is performed.

The editorial tosses in a practical argument: "the broader the parameters for partial match searches, the more likely false positives become." But what is a "false positive" here? It is not a false conviction. If a close relative did not deposit the crime-scene DNA, then it is improbable that DNA testing of this individual will establish a total match. Testing a falsely identified relative thus will exculpate him. This is not to denigrate the individual's interest in not becoming a "person of interest" to the authorities, even if the interest is temporary, but such false leads are also a concern for the police because they waste time and resources. If the parameters are set so wide as to include large numbers of false leads, then the police will find the technique frustrating, and it will not be used very often. Furthermore, even if the "parameters" were grossly overinclusive, producing many bad near-matches, most of the false leads could be detected in the laboratory with the existing samples from the crime and the nearly matching convicted offenders. If a brother, son, or father of an actual rapist is in the offender database, then he will have the same Y chromosome as the rapist. If the samples do not match at loci on the Y chromosome, then the near-miss offender can be crossed off the list.  In this way, false leads to close relatives of an individual in the database can be largely eliminated by testing at Y-STRs or Y-SNPs in rape cases (or others with male offenders).

Professor Mnookin concludes that "as a matter of fairness, it ought to be all or nothing." Does this mean that (1) either everybody should be in the law-enforcement identification databases or nobody should be, or rather that (2) either everybody should be in the law-enforcement identification databases or only convicted offenders should be? Whichever is intended, she is right about one thing -- near-miss searching is a step in the direction of a more universal database.

DHK

April 8, 2007 | Permalink | Comments (2) | TrackBack