Jim Harper Responds to My Comments on Fingerprinting Foreigners at the Border
Anyway, turning someone away from the border is a trivial security against terrorism because terrorists are fungible. Turning away a known terrorist merely inconveniences a terrorist group, which just has to recruit someone different. The 9/11 attacks were conducted for the most part by people who had no known record of terrorism and who arrived on visas granted to them by the State Department. Biometric border security would have prevented none of them entering.
(Another option is physical avoidance of the border—crossing into the United States from Canada or Mexico at an uncontrolled part of the border. I know of no instance of this occurring (successfully), but it could. And, most importantly, there’s no cost-effective way to prevent it.)
In summary, border biometrics have some benefit! They are at best a mild inconvenience to terrorists—an inconvenience that the 9/11 attacks mostly anticipated. But that’s not zero benefit! It’s just negligible benefit.