Mr. Puccio won stunning convictions of Senator Harrison A. Williams Jr., a New Jersey Democrat, and several members of the House of Representatives who were videotaped taking bribes from an undercover agent posing as an Arab sheik. He parlayed those successes into a lucrative practice defending the wealthy, powerful and often unpopular. His greatest success was the 1985 acquittal of Mr. von Bülow, a Danish-born socialite, in a second trial on charges of twice trying to kill his wife, Martha, with insulin injections at their mansion in Newport, R.I., in 1979 and 1980. Mrs. von Bülow, an heiress to a $75 million fortune who was known as Sunny, lapsed into a coma that left her in a vegetative state until she died in 2008. Thomas Phillip Puccio was born on Sept. 12, 1944, in Brooklyn, the only child of Matthew and Jeanette Puccio. His father was a federal purchasing supervisor and his mother a secretary. He grew up in Brooklyn, attended Brooklyn Preparatory School and graduated from Fordham University in 1966 and from its law school in 1969. Mr. Puccio’s first marriage, in 1976 to Carol L. Ziegler, a lawyer and teacher, ended in divorce. The couple had one son, Matthew, who drowned in 1995 at age 16 when a car in which he was learning to drive, accompanied by his father, plunged into a yacht basin in Westport, Conn. Mr. Puccio escaped, but his son became trapped behind the steering wheel. Mr. Puccio, who lived in Weston, married his second wife, the former Kathryn Thayer, in 1992. She is his only immediate survivor.