Who is F. Denton Voyles from The Pelican Brief and what is their importance?

F. Denton Voyles is the Director of the Federal Bureau of Investigations (FBI), Voyles is portrayed as gruff, blunt, sneering, stocky, trench-coated, gum chewing, cigar smoking man worrying about a second heart attack. He has served under three presidents and has no respect for the current one, who lets his hated Chief of Staff, Fletcher Coal, push him around.