I am reading an interesting book about the US Mexican Border, written by Tim Gaynor, a Reuters Reporter who spent years along the border and was named the 2007 Reuters Journalist of the Year for his immigration coverage.
In his book, Tim describes the IDENT system which is used to screen anyone arriving in the US by checking the arriving person's two index fingers against an immigration database. This is the first biometrics system going down a path of ever greater investigation available to all border stations and airports.
Another system also in use behind the scenes is the Automated Fingerprinting Identification System (IAFIS), which is a more thorough check that reads all ten digits and matches them against law enforcement databases. It is about the size of a tissue box. A detainee's thumbs are run over rollers and held against a flat pane of glass on top of the box, where they are photographed by a digital camera. Then all four fingers on each hand are wiped and held up against the glass and are photographed in turn.
"The IAFIS program scans the unrepeatable sequence of nodes and intersections in each of the prints and transforms it into a numerical code. The results are then matched with data held digitally in a live crime database held by the National Crime Information Center (NCIC) that holds information from federal. state, and local law enforcement throughout the US, as well as details on suspects, criminals, and fugitives sought by Interpol." Midnight on the Line, pg. 90.