Neal, working in Nashville, went on to a busy career in private practice, representing clients that included Exxon, Johnny Cash and Elvis Presley's doctor. He died at a Nashville hospital Thursday of cancer of the esophagus, The Washington Post reported.
A native of Tennessee, Neal grew up on his family's farm near Oak Grove and graduated from the University of Wyoming and Vanderbilt Law School. He was working for the Justice Department when Attorney General Robert Kennedy selected him in 1961 to investigate Hoffa, and he eventually won a conviction for jury tampering three years later.
"Jimmy Hoffa once called me the most vicious prosecutor who ever lived," Neal told an interviewer.
Special Prosecutor Archibald Cox brought Neal into the Watergate investigation. He got a guilty plea from John Dean and prosecuted John Mitchell, John Ehrlichman and H.R. Haldeman.
He was often successful as a defense lawyer, winning acquittals for Ford Motor Co. in a criminal case over the Pinto and for Presley's doctor. But one client, Exxon, ended up with the largest civil judgment up to that point, $20 billion, for the Valdez spill.
Fortune magazine named him one of the Top 5 U.S. trial lawyers in 1985.
Neal played a lawyer in a 1980s TV movie, "Murder in Coweta County." The role was arranged by Johnny Cash.