Former head of the Boston Federal Bureau of Investigation Kenneth Kaiser plead guilty in federal court on Thursday to the charge that he had illegal contacts with the bureau after he retired. He had meetings with agents as a private consultant.

Kaiser was released on personal recognizance and prosecutors are recommending that he pay a $15,000 fine and serving no prison time. Based on the charges, an ethics violation usually warrants up to one year in prison and a maximum fine of $100,000.

An ethics law prohibits professional contact from senior executive branch personnel with the agency they were employed with for one year after they leave the office.

Anthony Fuller, Kaiser’s defense attorney, said in a Thursday statement that Kaiser’s communications to FBI employees were not meant to be secretive.

“All of his communications to his former colleagues in the FBI were made in the good faith that he was helping their law enforcement mission,” he said. “He did not contact his former colleagues through secret means or back channels but did so openly and obviously and, in one instance, attended a meeting inside the U.S. Attorneys office in Boston.”

Kaiser is scheduled to be sentenced on Dec. 17.

More details to come.