A former top lawyer for the New York Police Department, Stephen Hammerman, who was commended by Police Commissioner Raymond Kelly for his role in handling the protests at the 2004 Republican convention, may soon have the FBI knocking on his door.

The FBI is investigating allegations of civil rights violations by New York Police Department personnel. A lawyer for several protesters, Gideon Oliver, said yesterday he would push to have the former deputy commissioner of legal affairs investigated for his role in the arrests, based on Mr. Hammerman’s actions as documented in video evidence.

Mr. Hammerman, now the senior special counsel for the New York office of the London-based law firm Clifford Chance, helped draft detailed arrest procedures for the convention. In the video footage, which is of uncertain origin, he is said to be seen ordering the arrest of one protester, Dennis Kyne, 36, a 15-year Army veteran, who is represented by Mr. Oliver.

FBI investigators this week wrote to Mr. Oliver, requesting an interview with him and his client about the August 31, 2004, arrests outside the New York Public Library. All seven charges – three for blocking traffic and four for disorderly conduct – against Mr. Kyne were dropped after the footage was seen in court, but not before a police officer, Matthew Wohl, testified that Mr. Kyne was resisting arrest and had to be dragged away by three officers. The video shows Mr. Kyne leaving the scene by himself, but yelling obscenities and calling the officers “Nazis.”

Mr. Oliver said the case showed the officer had committed perjury.

The FBI investigation comes a week after the Civilian Complaint Review Board sent a letter to Mr. Kelly criticizing the actions of his department.

The commissioner immediately fired back a letter, saying the board ignored the department’s success in maintaining order during one of the largest protests in the city’s history. The mayor and other city officials consistently have praised the department’s handling of the convention.

“It’s a major breakthrough when the FBI says they are criminally investigating the NYPD,” an associate legal director at the NYCLU, Christopher Dunn, said.

Mr. Hammerman said yesterday that allegations that he acted inappropriately were “nonsense.” A spokesman for the police department, Paul Browne, said in a statement that the NYPD is cooperating with the FBI investigation.

In addition to the FBI, the Manhattan district attorney’s office and the police department’s Internal Affairs Bureau also are looking into the matter.