Overseas, Israel's Ministry of Defense uses facial scanning to monitor movement along the Gaza Strip. A scruffy district in London uses them to remotely patrol the streets. Mexico and Uganda use them to register voters. The facial scans work by converting images into numerical codes that can be easily stored and searched in large databases.
Proponents say they are less intrusive than other biometric scans and highly effective.
But some experts say the technology is inaccurate, which can lead to misidentifications. Click here to go to this article.