The city had sought to keep secret field intelligence reports prepared by undercover police officers, but U.S. Magistrate Judge James C. Francis IV called for the city to turn over those and other documents to lawyers representing hundreds of protesters challenging their arrests.

For the most part, Francis rejected city arguments that the documents were not relevant and were protected by law enforcement privilege. He did, however, say some documents and information were not pertinent and could be withheld or redacted.

Francis said they could be released in redacted form to hide the identities of undercover officers and confidential police tactics and strategies.

“Information is not privileged simply because it was obtained as a result of an undercover investigation,” he wrote. “Information is privileged only when its disclosure would interfere with legitimate law enforcement interests.”

More than 1,800 people were arrested at the four-day convention at Madison Square Garden, where President Bush accepted his party’s nomination for a second term in office.

The New York Civil Liberties Union filed the lawsuit on behalf of some of those detained, saying the arrests violated the protesters’ civil rights.

Court documents have shown that arrested protesters were held before their initial court appearances for up to six times longer than those arrested on charges unrelated to the convention.

The NYCLU argues the delays were a deliberate policy decision to keep protesters off the streets. The police contend the delays were few and were caused by a high number of arrests in a short amount of time.

Peter Farrell, a senior counsel in the city law office, said the city would decide whether to appeal after “reviewing the information the judge has ordered produced to determine whether the disclosure will compromise the programs or personnel of the NYPD Intelligence Division.”

Christopher Dunn, associate legal director at the NYCLU, said he expected the NYCLU would receive some of the documents within 10 days unless the city appealed.

“We believe these documents will reveal not only the vast scope of the NYPD’s political surveillance operation but also that there was no need for the Police Department’s harsh treatment of protesters,” he said.