CLARKSBURG, W.Va. — The FBI is embarking on a $1 billion effort to build the world’s largest computer database of people’s physical characteristics, a project that would give the government unprecedented abilities to identify people in the United States and abroad.

Images of faces, fingerprints and palm patterns are flowing into FBI systems in a climate-controlled, secure basement in Clarksburg.

Next month, the FBI will award a 10-year contract that would significantly expand the amount and kinds of biometric information it receives.

And in the coming years, law-enforcement authorities worldwide will be able to rely on iris patterns, face-shape data, scars, and perhaps even the unique ways people walk and talk to solve crimes and identify criminals and terrorists.

The FBI also will retain, upon request by employers, fingerprints of employees who have undergone criminal-background checks so the employers can be notified if employees have brushes with the law.

“Bigger. Faster. Better. That’s the bottom line,” said Thomas E. Bush III, assistant director of the FBI’s Criminal Justice Information Services Division, which operates the database from its headquarters in the Appalachian foothills.

The increasing use of biometrics is raising questions about how Americans can avoid unwanted scrutiny.

Biometrics criticized

It is drawing criticism from those who worry that people’s bodies will become de facto national identification cards. Critics say that such initiatives should not proceed without proof that the technology — which has raised doubts in a German study — really can pick a criminal out of a crowd.

In 2004, the Electronic Privacy Information Center objected to the FBI’s exemption of the National Crime Information Center database from a Privacy Act requirement that records be accurate. The group noted that the Bureau of Justice Statistics in 2001 found the system was “not fully reliable” and that files “may be incomplete or inaccurate.”

FBI officials justified that exemption by noting that it is “impossible to determine in advance what (law enforcement) information is accurate, relevant, timely and complete.”

Privacy advocates worry about the ability of people to correct false information. “Unlike say, a credit-card number, biometric data is forever,” said Paul Saffo, a Silicon Valley technology forecaster.

He said he feared that the FBI, whose computer technology record has been marred by expensive failures, could not guarantee the data’s security. “If someone steals and spoofs your iris image, you can’t just get a new eyeball,” Saffo said.

The use of biometric data is increasing throughout the government.

For two years, the Defense Department has been storing images of fingerprints, irises and faces of more than 1.5 million Iraqi and Afghan detainees, Iraqi citizens and foreigners who need access to U.S. military bases. The Pentagon also collects DNA samples from some Iraqi detainees.

Airports using iris scans

The Department of Homeland Security has been using iris scans at some airports to verify the identity of travelers who have passed background checks and who want to move through lines quickly.

In an underground facility the size of two football fields, a request reaches an FBI server every second from somewhere within the United States or Canada, comparing a set of digital fingerprints against the FBI’s database of 55 million sets of electronic fingerprints. A possible match is made or ruled out as many as 100,000 times a day.

In the first large-scale, scientific study on face recognition, the German government this year found that the technology, while promising, was not effective enough for use by police.

The technology was able to match travelers’ faces against a database of volunteers more than 60 percent of the time during the day, when the lighting was best. But the rate fell to 10 to 20 percent at night.