A former office operations manager at Morrison & Foerster pleaded guilty Wednesday in Washington’s federal district court to felony mail fraud for using a law firm credit card to make hundreds of thousands of dollars in unauthorized personal purchases.

Andrew Robertson, who worked for Morrison & Foerster at offices in Washington and Virginia, will be sentenced in August before U.S. District Judge Colleen Kollar-Kotelly of the District of Columbia. Robertson, appearing via video Wednesday, admitted he used a law firm card to make at least $425,000 in retail and other purchases unrelated to the business of the major U.S. law firm.