She previously served as an Assistant United States Attorney in the Eastern District of New York from 1991 to 2005. In this position, she served as the Chief of Narcotics and General Crimes Units, as well as Deputy Chief of Public Corruption and Violent Crimes Units. Margaret also was S. Assistant U.S. Attorney for United States District Court for the Eastern District of New York from 2014 to 2015. Prior to becoming a prosecutor, Margaret was an associate at Milbank Tweed Hadley & McCloy.