A lawyer for the Kings County District Attorney said yesterday that an investigation into Charles Hynes’s 2001 political opponent had the effect of encouraging, not ending, the challenger’s political activity.

Mr. Hynes’s opponent in the 2001 Democratic primary, Sandra Roper, sued Mr. Hynes last year, claiming the district attorney sought retribution by opening an investigation into allegations she stole from a client. Ms. Roper is not the first to allege that Mr. Hynes has used the criminal justice system to instill fear in his political opponents.

Efforts by the city’s lawyer for Mr. Hynes, Eamonn Foley, to have the suit dismissed prompted lawyers for both sides to debate Ms. Roper’s claims for the first time. In U.S. District Court in Manhattan yesterday, Mr. Foley questioned whether the investigation did indeed discourage her from engaging in politics, as her lawyer, Ezra Glaser, claimed. Mr. Foley asserted that Ms. Roper emerged from the legal battle with a renewed commitment to stay active in politics.

“She was fired up and continued to run for other offices,” Mr. Foley said.

Ms. Roper, who had not previously been involved in politics, has since unsuccessfully run for a seat in the state Assembly and for a civil court judgeship.

An independent prosecutor ultimately investigated Ms. Roper on charges of larceny and forgery. Ms. Roper, who was charged but not convicted, claims the district attorney’s office is responsible for starting the investigation.

Mr. Hynes’s office declined to comment. Last year, Mr. Hynes told the New York Times: “Obviously, I could not investigate someone who is running against me.”

Judge William Pauley III of U.S. District Court seemed interested in Mr. Hynes’s alleged involvement in the matter. He interrupted Mr. Foley three times as the lawyer argued that Mr. Hynes should not be sued.

“Wasn’t District Attorney Hynes alleged to be the catalyst for the special prosecutor?” Judge Pauley asked.

He said he would decide whether to allow the suit to proceed.