“All our activities were legal and were subject in advance to Handschu review,” Mr. Browne said.

Before monitoring political activity, the police must have “some indication of unlawful activity on the part of the individual or organization to be investigated,” United States District Court Judge Charles S. Haight Jr. said in a ruling last month.

Christopher Dunn, the associate legal director of the New York Civil Liberties Union, which represents seven of the 1,806 people arrested during the convention, said the Police Department stepped beyond the law in its covert surveillance program.

“The police have no authority to spy on lawful political activity, and this wide-ranging N.Y.P.D. program was wrong and illegal,” Mr. Dunn said. “In the coming weeks, the city will be required to disclose to us many more details about its preconvention surveillance of groups and activists, and many will be shocked by the breadth of the Police Department’s political surveillance operation.”

The Police Department said those complaints were overblown.

On Wednesday, lawyers for the plaintiffs in the convention lawsuits are scheduled to begin depositions of David Cohen, the deputy police commissioner for intelligence. Mr. Cohen, a former senior official at the Central Intelligence Agency, was “central to the N.Y.P.D.’s efforts to collect intelligence information prior to the R.N.C.,” Gerald C. Smith, an assistant corporation counsel with the city Law Department, said in a federal court filing.

Balancing Safety and Surveillance

For nearly four decades, the city, civil liberties lawyers and the Police Department have fought in federal court over how to balance public safety, free speech and the penetrating but potentially disruptive force of police surveillance.

After the Sept. 11 attacks, Raymond W. Kelly, who became police commissioner in January 2002, “took the position that the N.Y.P.D. could no longer rely on the federal government alone, and that the department had to build an intelligence capacity worthy of the name,” Mr. Browne said.

Mr. Cohen contended that surveillance of domestic political activities was essential to fighting terrorism. “Given the range of activities that may be engaged in by the members of a sleeper cell in the long period of preparation for an act of terror, the entire resources of the N.Y.P.D. must be available to conduct investigations into political activity and intelligence-related issues,” Mr. Cohen wrote in an affidavit dated Sept. 12, 2002.