Duff was born in New Orleans, Louisiana and has written plays and television screenplays for films such as the television drama Doing Time on maple Drive (1992, starring James B. Sikking and Bibi Besch), the television movie Without a Kiss Goodbye (1993, with Gwynyth Walsh and David Ogden Stiers), the drama Betrayed: A Story of Three Women (1995), as well as for several television series, including Popular, The Agency, J.J. Abrams' Felicity (2001), and The D.A. (2004), for which he also served as executive producer.