William G. Harrington, 68, prolific mystery writer who also collaborated on books with celebrity authors. Harrington wrote 25 books, including "The English Lady," published in 1982 to strong reviews. He also wrote a series of six novels featuring Columbo, the rumpled television detective played by Peter Falk in the long-running series. He contributed research to books written by such authors as Harold Robbins, Margaret Truman and Elliott Roosevelt. The son of an oil producer born in Marietta, Ohio, he was educated at Duke University and Ohio State University, where he earned a law degree. He practiced law for 20 years beginning in 1958 but produced books at a steady pace. His titles include "Which the Justice, Which the Thief," "The Jupiter Crisis," and "The Cromwell File." He began to write full time in 1980. Police described his death Nov. 8 in Greenwich, Conn., as an apparent suicide.