Professor Gwen Stern Trains Supervising Prosecutors through National Institute for Trial Advocacy June 17, 2010 Professor Gwen Stern trained supervisors in the Philadelphia Office of the District Attorney on June 11-12. As an instructor with the National Institute for Trial Advocacy, Stern taught supervisors how to train and groom newly minted district attorneys. Stern directs the law school’s Trial Advocacy Program as well as the Marshall-Brennan Constitutional Literacy Project.