Database aggregators such as ChoicePoint have quietly become powerful arbiters, whirring in the background when people seek jobs, get on airplanes, apply for insurance, commit a crime or fall victim to one. ChoicePoint's computers are packed with 19 billion public records.

....Since being spun off in 1997 from credit giant Equifax Inc., Alpharetta, Ga.-based ChoicePoint has become an $800 million institution that acquires a company - along with its data trove - every two months. ChoicePoint owns a DNA analysis lab, facilitates drug testing for employers and recently began selling background-checking CD-ROMs at Sam's Club.

But Smith says ChoicePoint is careful in its choices. For example, he says he opposes three data-mining projects that have alarmed civil libertarians: the Pentagon's now-quashed Total Information Awareness system, the CAPPS II airline passenger screening system and the Matrix multistate crime and terrorism network. CAPPS and Matrix get data from ChoicePoint rivals.

To Smith, each follows a flawed model: assembling a huge pool of data on people and then mining it to look for suspicious patterns or evidence that might be relevant to a case.

Instead, Smith believes disparate collections of data should remain separate until an investigator has probable cause to put the pieces together.

Last year, a furor erupted in Latin American countries when The Associated Press reported that ChoicePoint had sold their citizens' home addresses, unlisted phone numbers and other personal information to the U.S. government. U.S. agencies used the data to track immigration violators and crime suspects.

ChoicePoint responded by deleting many of the files.

The company also took heat after a firm it had acquired, DBT Online Inc., supplied Florida elections officials with an inaccurate list of felons - the roster included some people with misdemeanors. Those names were purged from voter rolls before the 2000 elections.