Mr. Haynsworth has practiced labor law since 1960. He is past president of the South Carolina Bar and the Greenville County Bar. Mr. Haynsworth is listed in the labor and employment law section of the 2004-2005 edition of The Best Lawyers in America and has been listed for over 20 years in all 11 editions of Best Lawyers.

Mr. Haynsworth is a permanent member of the Fourth Circuit Judicial Conference. From 1996-2002, he served as a member of the Fourth Circuit Advisory Committee on Rules and Procedures, and in 2001, he was appointed to serve as chair of the committee. The Fourth Circuit is composed of all federal courts in the states of South Carolina, North Carolina, Virginia, West Virginia, and Maryland. The Advisory Committee studies the court's local rules and internal operating procedures and makes recommendations concerning them. There is only one attorney from each of the five states who serves on this committee, and members serve for three-year terms and are eligible for reappointment.