Joseph Petersen, a former research analyst in the N.S.A., pleaded guilty to espionage. He worked for the Dutch, who had learned from him that the U.S. had cracked Dutch codes.

In the U.S. District Court at Alexandria, Va. last week, Joseph Sydney Petersen Jr., 40, a gangling, cross-eyed former research analyst in the National Security Agency, the Government’s topmost secret hive of codebreakers and message-interceptors, pleaded guilty to espionage.

Two months ago, Petersen’s lawyer leaked the information that his client,…