A 55-year-old American University law school professor was found dead in his Northwest Washington town house apartment yesterday afternoon, apparently killed during a burglary, homicide investigators said.

Norman Smith Penney, a professor at Washington College of Law, part of American University, was found in his ransacked home at 1616 Belmont St., according to D.C. police homicide Lt. Carl Alexander.

Alexander declined to say who notified police or how Penney was killed, but sources familiar with the investigation said Penney was found by a security guard of the town house and apartment complex, called Beekman Place.

Penney was found fully clothed and gagged, with his hands and feet tied, according to police sources. There were no outward signs of injury, indicating that Penney may have been strangled or asphyxiated.

Penney, who had been seen at American University Tuesday afternoon grading papers, was pronounced dead at his home.

If it is determined that Penney was strangled or asphyxiated by the gag, it would be the third such death during a burglary in that area in the last six weeks, police said.

On Nov. 13, the body of 83-year-old Norma Remington was found bound and gagged at 1324 Otis Pl. NW. Her home was burglarized. On Christmas day, the body of Naomi Buckner, 73, of 3155 Mount Pleasant St. NW., was found bound and gagged on her living room floor. All three incidents occurred within a one-mile radius.

Washington College of Law Dean Thomas Buergenthal said Penney, who had moved to Washington this year from Ithaca, N.Y., was "an outstanding teacher, lawyer and scholar, one of the leading lawyers on commercial and international law." Buergenthal said Penney, a 1953 Cornell University law school graduate, had been teaching at Cornell until this fall. He had been in private practice in Buffalo, and was one of the U.S. delegates to the United Nations Commission on International Trade Law. He was a Fulbright Scholar and had lectured at numerous universities around the world.