The Los Angeles Police Department is experimenting with facial-recognition software it says will help identify suspects, but civil liberties advocates say the technology raises privacy concerns and may not identity people accurately.

A highly advanced system of video surveillance that Chicago officials plan to install by 2006 will make people here some of the most closely observed in the world.

New high-tech passports may never provide the hoped-for level of protection against terrorists because the key technology - facial recognition - requires technologies that even proponents say are difficult to implement and not yet reliable.

Face-recognition technology, often touted as a promising tool in the fight against terrorism, earned a bad reputation after it failed miserably in some well-publicized tests for picking faces out of crowds. Yet, on simpler challenges, the technology's performance is improving and business has been growing.

Computer scientists, attempting to design machines that can pick out objects in images, have found that faces are a major challenge.

Security experts have high hopes that facial-recognition systems can weed out terrorists and criminals, making airports and other public places safer. But the controversy over tests at Boston Logan's airport shows that the reliability of such systems are still in dispute.

The author examines the legality and social costs of the Shot Spotter and FaceIt, two recent law enforcement inventions that have been implemented to mass monitor the public. He probes the Constitutionality of these technologies and whether they have blurred the distinction between what is public and private and offers policy prescriptions for restoring the balance.

Iris-scanning and face-matching technologies don't work nearly as well as their manufacturers have claimed, the Department of Defense has discovered.

Since Sept. 11, discussion of the disputed technology of face recognition has focused on its potential for identifying criminals and terrorists — and for invading citizens' privacy. But in England, the police are pursuing a different path: they want to use facial recognition software to identify crime victims.

The American Civil Liberties Union issued a report Thursday saying use of face-recognition technology failed miserably in a Tampa, Fla., trial last year. The ACLU says police logs show the system did not identify a single criminal during two months of use and was eventually abandoned by police there.