The Transportation Security Administration is expanding its screening of passengers before they arrive at the airport by searching a wide array of government and private databases that can include records like car registrations and employment information. It is unclear precisely what information the agency is relying upon to make these risk assessments, given the extensive range of records it can access, including tax identification number, past travel itineraries, property records, physical characteristics, and law enforcement or intelligence information. The measures go beyond the background check the government has conducted for years, called Secure Flight, in which a passenger's name, gender and date of birth are compared with terrorist watch lists. Now, the search includes using a traveler's passport number, which is already used to screen people at the border, and other identifiers to access a system of databases maintained by the Department of Homeland Security. I think the best way to look at it is as a pre-crime assessment every time you fly," said Edward Hasbrouck, a consultant to the Identity Project, one of the groups that oppose the prescreening initiatives. "The default will be the highest, most intrusive level of search, and anything less will be conditioned on providing some additional information in some fashion." Critics argue that the problem with what the agency calls an "intelligence-driven, risk-based analysis" of passenger data is that secret computer rules, not humans, make these determinations. Civil liberties groups have questioned whether the agency has the legal authority to make these assessments.