In the aftermath of the terrorist bombing—no lesser word will do—at the Boston Marathon, a major debate has broken out over the proper law enforcement procedures in two key areas: general surveillance and targeted searches. Many insist that a general right to privacy should limit the first, and that concern with racial and ethnic profiling should limit the second. Both of these overinflated concerns should be stoutly resisted.

The task of unearthing terrorist activities is like looking for a needle in the haystack. Even the best system of oversight and surveillance will turn up an extraordinarily high percentage of false positives, for the simple reason that the odds of any given lead providing useful information, although hard to estimate, may be very small. It takes, therefore, a very large payoff indeed to justify government action in those cases, which is why police surveillance and monitoring should receive high priority only in cases where the risk justifies the large public expenditures and the serious intrusions on privacy of those targeted individuals. At this point, the questions arise of what kind of surveillance should be used, and when and how law enforcement officials can target particular individuals.

The Way Forward on Surveillance

The Tsarnaev brothers’ attack at the Boston Marathon has brought forth an insistent public call for an increase in surveillance to detect suspicious activities before it is too late. To be sure, there are always technical difficulties in using surveillance devices. But any objection on that ground should be treated solely as means-ends questions, which can in large measure be answered by improved software in such key areas as facial recognition detection. The moral, social, and constitutional objections are sadly misplaced.

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