William P. Lynch, 56, a Washington lawyer who had been an assistant vice president of the District Realty Title Insurance Corp. since 1981, died May 15 at George Washington University Hospital after a heart attack. He lived in Bethesda.

Mr. Lynch was born in Brooklyn, N.Y. He served in the Army during the conflict in Korea. A graduate of St. John's University in New York, he earned a law degree from the University of Baltimore.

In 1958, he moved to Washington and joined the FBI as a special agent. During the 1960s, he was a sales representative with the Bogart and Brownell Insurance Co. in Bethesda.

Mr. Lynch had a private law practice specializing in real estate from 1969 to 1981. During the mid-1970s, he also taught criminal evidence at Montgomery College. From 1981 until his death, he had worked for District Realty.

He was a member of the Rock Creek Council of the Knights of Columbus, the Society of Former Special Agents of the FBI, and the Congressional Country Club. He also belonged to St. Jane de Chantal Catholic Church in Bethesda and had served on the board of the Catholic Youth Organization.

Survivors include his wife, the former Catherine Cabot, of Bethesda; three daughters, Kathleen M. Prestemon of Rockville, Mary A. Tormoehlen of Crothersville, Ind., and Helen Lynch of Bethesda; four sons, Navy Lt. Joseph M., who is serving aboard the aircraft carrier Nimitz, near Israel, William P., of Hagerstown, and Thomas E. and Richard O., both of Bethesda, and two grandchildren.