Iris Scan
The Eyes Have It
Probably the most foolproof biometric measure is the eye's iris. Its complex pattern of zigzagging lines and random dots is much more distinctive than the whorls of a fingerprint.
In fact, because authorities in a few foreign countries are confident that iris scans can't be circumvented, they're starting to allow airlines to use iris scanning at selected airports. For the airlines, it's a perquisite for frequent fliers: If people register their iris scans, they can bypass the usual security check.
Currently, a person's eye must be in close to the scanner. Intelligence and law-enforcement agencies hope that some way can be found to scan irises from a distance -- or even to spot a suspect in a crowd.