Only a fool with no sense of history would have been sanguine about the prospects for civil liberties after the September 11 attack. Whenever Americans have felt frightened or under siege they have responded by persecuting immigrants, members of suspect ethnic groups, or others guilty only of real or apparent sympathy for unpopular ideologies. Our most revered, or at least respected, presidents have been among the worst offenders: John Adams supported the Alien and Sedition Acts, which criminalized opposition to the government (and was used to imprison his political foes); Abraham Lincoln suspended habeas corpus and presided over the arrests of thousands of people for crimes like "disloyalty" (which sometimes consisted of criticizing the president); Woodrow Wilson imprisoned Eugene Debs for speaking out against America's entry into the First World War; Franklin Roosevelt famously and shamefully interned Japanese-Americans during World War II. Liberty was trampled by all of these measures, while security was enhanced by none of them.

But the cruelty and folly of imprisoning people for their political views or their ethnicity is usually acknowledged only in hindsight. During World War II some people no doubt felt safer knowing that their Japanese-American neighbors were interned. The Supreme Court ruled at the time that the internment was justified on national security grounds. People felt safer last fall when the Bush administration swept up and detained over one thousand immigrants in the wake of the September 11 attack, even though the vast majority of them had no apparent connection to terrorism. History shows that frightened people tend to assume that restrictions on liberty make them safe. They support repressive measures instinctively in the expectation that other people will be targeted by them, and ask questions only decades later.

Consider the false promise of many electronic surveillance measures, like facial recognition systems. A recent report by the American Civil Liberties Union reveals that the widely publicized facial recognition system used on the streets by police in Tampa, Florida, "never identified even a single individual contained in the department's database of photographs." Instead, "the system made many false positives, including such errors as confusing what were to a human easily identifiable male and female images." The ACLU report was based on a review of police logs obtained through Florida's open-records law.

Technological inaccuracies like these were coupled with human errors and abuses of discretion. A facial recognition system can only be as good as its database in identifying terrorists or other violent criminals, and in Tampa the photographic database was not limited to known criminals: it included people the police were interested in questioning in the belief that they might have "valuable intelligence." Under guidelines like this ordinary law-abiding citizens who venture out in public might find themselves setting off alarms in facial recognition systems (should they ever work properly).

Whether or not your photograph is in the database, your privacy is likely to be invaded by a facial recognition system. Cameras scan crowds and, as the ACLU observes, in Britain, where electronic surveillance is becoming routine, camera operators are apt to focus disproportionately on racial minorities or while away the hours peering up women's skirts. In Michigan, according to a report by the Detroit Free Press, police used a database to stalk women and intimidate other citizens.

Considering the ways facial recognition systems have been used and abused so far, it's fair to say that they constitute a threat—to privacy, liberty, and even physical safety—not a promise of security. But we are beginning to use them more, not less. Several cities have decided to deploy the kind of system that failed so miserably in Tampa, and of course, facial recognition is being touted as an important airport security tool. Airports in cities including Boston, Providence, and Palm Beach are installing facial recognition systems. Meanwhile precautions that might actually enhance security, like screening all checked bags and carry-ons, are as far from implementation as ever.

Why do a majority of American tolerate and support invasive or repressive faux security measures? I suspect we're simply too frightened and uninformed to challenge them. People who want or need to continue flying, for example, can't bear to devote much thought to the continuing inadequacies of airport security; instead they take comfort in whatever false promise of security they're offered. So, the problem for civil libertarians isn't the tendency of people to trade liberty for security. It's their tendency to trade liberty for mere illusions of security. Liberty would benefit greatly from a logical, pragmatic approach to safety. In our frightened, irrational world, freedom may be threatened most by wishful thinking.