In fact, the necessary equipment is not even installed in vehicle lanes along the border.
Government officials told The Associated Press that checking more people would create too big a backup at the border, where hours-long traffic jams are already common.
Some members of Congress who voted for the system in 1996 are complaining they were misled. They said the intent was to use biometrics - or a person's unique physical traits - to screen everyone.
"Congress would not have gone to the trouble of requiring biometric features on the border crossing card if it knew the administration would not require that those features be read by scanners," said Rep. Lamar Smith, R-Texas, who wrote the legislation.
The U.S. government has spent tens of millions of dollars issuing visa cards digitally embedded with the holder's photo and fingerprints.
Holders of the cards come across the border tens of millions of times each year. But on average, in only about 2 percent of those cases are the cardholders screened with the biometric technology to verify their identities and check law-enforcement records, said Paul Morris, Customs and Border Protection's executive director of admissibility requirements and migration control.
The checks are done consistently only on the small portion of cardholders who seek permission to travel beyond the border region.
"As the technology becomes available, we can expand the current level of biometric matching," Morris said. "There is not a technology solution currently available that will not cause delays that are well beyond the acceptable levels." Beginning in 1998, the high-tech "laser visas" have been issued to 9.1 million Mexicans for short visits to the United States. The laser visas, which look like driver's licenses, have a 1.4-inch optical memory stripe holding personal information such as name, gender and birth date. The stripe also stores the owner's digitized facial photo and two fingerprints. Cardholders coming across the border may be asked to press their fingers against a glass and pose for a photo, while their card pulls up their biometric file - a process that takes an extra 30 seconds or so per person. The photo and fingerprints can also be instantly checked against criminal and terrorist watch lists. The laser visas entitle Mexicans to travel 25 miles from the border - slightly farther in Arizona - for 30 days. Cardholders can also apply for a permit to travel anywhere in the U.S. for up to six months. Border inspectors routinely swipe the laser visas through a machine to retrieve the basic personal information and to call up a photo. But, with some exceptions, the inspectors use the facial- and fingerprint-matching technology only for those applying at the border for one of the six-month permits, Morris said. That practice means that most of those who are checked are not selected at random; they know they are going to be scanned when they come across. The government contract for laser visas was worth $28.6 million from 2000 to 2006, and Homeland Security awarded a five-year renewal in March to General Dynamics Corp. worth $28.5 million, according to Homeland Security. That price tag excludes the cost of opening new consulates to handle the rush of applicants. The State Department established consulates across the border from Laredo, Texas, and Nogales, Ariz. In Tijuana, Mexico, the consulate took over an old gymnasium across town. The 1996 law said anyone presenting a border crossing card "is not permitted to cross over the border into the U.S. unless the biometric identifier contained on the card matches the appropriate biometric characteristics of the alien." But Sandra Raynes, consular officer at the U.S. consulate in Tijuana, said: "If they were to check everyone, you'd have lines all the way down to Cabo San Lucas," about 1,100 miles south of San Diego. U.S. officials said biometrics are only part of its effort to stem illegal crossings. An inspector's wits and agency intelligence are also key, they said. Biometrics "is one tool in our toolbox," said Kelly Klundt, a Customs and Border Protection spokeswoman. Also, the laminated cards have reduced fraud because they are difficult to counterfeit, officials said. Older visas looked like crumpled library cards, some dating to the 1950s. Authorities said women in their 60s used cards with photographs of teenage girls because the cards had no expiration dates. Former Rep. Jim Kolbe, a Republican who left Congress in January after 22 years representing a district on the Arizona border, said lawmakers expected checks on all cardholders, though there was no timetable. "We definitely intended to go further with it than we have," he said. "Ten years later, it seems incredible that we've only gotten this far with it." The 14 pedestrian booths at San Ysidro, the nation's busiest border crossing by far, are equipped with fingerprint glass but no cameras. But that glass is not used on the 30,000 people who walk though daily. There is neither type of equipment in the 24 vehicle lanes, which handle about 35,000 cars and 250 buses a day. Applicants for the six-month permits are asked to pull aside into a small parking lot, get out and walk up to a booth, where they are fingerprinted and photographed for verification. Initially, border crossings did not even have equipment to lift personal information off the cards, let alone the biometric data. Jeffrey Davidow, U.S. ambassador to Mexico from 1998 to 2001, recalls members of Congress visiting the border to see the machines, which were never used when the lawmakers were gone. "I'd tell them that it was all show, that it doesn't work, that the card is not doing what it's supposed to do," Davidow said. He said his warnings elicited shrugs. There were also technological setbacks. Equipment to verify photos and fingerprints often failed to read through sweat, scratches and other wallet "crud," according to an internal Homeland Security report. A test at five Texas crossings in the spring of 2004 showed that 731 out of 1,740 cards, or 42 percent, were unreadable, according to the report, which was provided to The Associated Press by someone who insisted on anonymity because the government did not authorize its release. Homeland Security officials did not have more recent figures on how many cards are correctly read. But they said technical problems have been resolved. AP-CS-05-15-07 1422EDT