One day in January 2003, an entrepreneur from Florida named Hank Asher walked into the Roosevelt Room of the White House to demonstrate a counterterrorism tool he invented after the Sept. 11, 2001, attacks. Soon to be called Matrix, it was a computer program capable of examining records of billions of people in seconds.

Accompanied by Florida Gov. Jeb Bush and the state's top police official, Asher showed his creation to Vice President Cheney, FBI Director Robert S. Mueller III and Tom Ridge, who was about to be sworn in as secretary of the new Department of Homeland Security, according to people at the meeting.

The demonstration startled everyone in the room who had not seen it before. Almost as quickly as questions could be asked, the system generated long reports on a projection screen: names, addresses, driver license photos, links to associates, even ethnicity. At one point, an Asher associate recalled, Ridge turned toward Cheney and nudged him with an elbow, apparently to underscore his amazement at the power of what they were seeing. A few months later, Ridge approved an $8 million "cooperative agreement" from his department to help states link to the computer system.

Yesterday, the American Civil Liberties Union asked the Homeland Security Department's chief privacy officer, Nuala O'Connor Kelly, to investigate the ties between the department and Matrix. The group said documents show that the federal government's involvement is deeper than previously known. The ACLU said the documents, obtained under the Freedom of Information Act, appear to show that the department helped manage the system, a role the ACLU said raises new questions about whether personal information is being used appropriately by law enforcement and intelligence officials.

One document, reported by the Associated Press yesterday, showed that Asher and his colleagues had created a list of 120,000 individuals with personal attributes that gave them a "high terrorist factor" score deemed worthy of extra attention from authorities.

"When the Department deeply involves itself in a program as fraught with significant privacy problems as the Matrix, your office must investigate," Barry Steinhardt, director of the ACLU's technology and liberty program, and a colleague wrote in a letter to Kelly.

Kelly said in an interview that she would be "happy to review the documents and the scope of the relationship."

"We try to be supportive of state and local homeland security efforts," she said, "but only with appropriate safeguards."

A continuing debate over the proper balance between privacy and security intensified when details of the Matrix system became public last summer. Matrix organizers, including intelligence officials in the Florida Department of Law Enforcement, said the system greatly enhanced the speed of investigations by combining government data with 20 billion commercial records about people.

Though they acknowledged at the time that the system could be abused, supporters said it enabled police, using data they had always had access to, to find patterns and links among people in seconds instead of months.

In the hours after the Sept. 11 attacks, Asher created a prototype at Seisint Inc., the Boca Raton, Fla., information service he founded. It generated the names of thousands of people he thought might be worth the attention of authorities. The tool called "high terrorist factor," which relied on intelligence and profiling, was later withdrawn from the system, Asher said.

The Florida Department of Law Enforcement soon became the lead agency in expanding Matrix and the Justice Department pledged $4 million to improve the system and widen its reach. Initially, 16 states agreed to contribute and draw information from Matrix, but 11 did not follow through or dropped out, citing civil liberties concerns or cost. Currently participating are Florida, Michigan, Ohio, Pennsylvania and Connecticut.

Organizers intend to ask other data services for proposals to create other Matrix-like systems later this year, in part to create competition, said Mark Zadra of the Florida department. Currently, Matrix operates under a sole-source contract with Florida.

Questions about Asher's past created controversy when the program became public last year. Confidential Florida police documents said he had been involved in drug smuggling in the early 1980s. Asher confirmed that he had limited involvement as a pilot for a few months, but police reports said he was never arrested or charged.

The ACLU and other critics say Matrix gives the government too much power to examine the lives of individuals through a process called data mining. Steinhardt said the government should not be deeply involved without a thorough examination of the implications. "It's a very dangerous marriage," he said.

Asher spent millions of his own money to refine the Matrix system. Asher said he wanted to find accomplices of the 9/11 hijackers and help authorities prevent terrorist attacks before they occur. He said Matrix does what authorities have repeatedly said needs to be done: connect the dots between suspects. "I did this because I thought we were in the middle of a world war," he said yesterday. "That it has drawn so much criticism makes me believe the country does not have its eye on the ball."

The White House meeting was a key moment for Matrix. Asher's work had already drawn the attention of senior authorities from the Justice Department, FBI, Secret Service and intelligence agencies by using Matrix to generate thousands of potential suspects, many of them Muslims.

Not long after the Sept. 11 attacks, Asher generated a list of 120,000 names, most of which he said had nothing to do with terrorism. Asher said he then cut it to about 1,200 names, something known as the "1 percent list," which provided leads in scores of investigations, some of which led to arrests.

Unknown to Asher at the time, he said, five of the names he generated were hijackers on the planes.