Like Thomas Jefferson, St. George Tucker was a Renaissance Man of the 18th century. While his professional career was in law and politics and he served as a highly respected legal professor and judge, he was also a prolific poet and inventor.
During the American Revolution, he served both as a smuggler and in the army, fighting at the Battle of Guilford Courthouse and at Yorktown, where he served on Washington's staff as a French interpreter.
So how did St. George Tucker end up on our list? Computer analysis of linguistic features of the text compared with samples of Henry's, Wirt's, and Tucker's writing by historian Steven Taylor Olsen tells us that Tucker is almost certainly the author of the version of Patrick Henry's "Liberty or Death" speech that we know today. (Source)
But when did he write it? Not in 1775, but years later, when William Wirt interviewed him for his Patrick Henry biography. The speech we accept today as the one Patrick Henry gave is based on St. George Tucker's memory.
Historians like David A. McCants believe,
Wirt was justified in placing great confidence in Tucker's reliability as a reporter. Tucker heard the speech as an impressionable youth who was without partisan political commitments.
Also, says McCants, Tucker's view of Henry was less idealized than Wirt's:
[H]is personal opinions towards Henry as a public leader and orator indicate that his judgments were not quick, nor static, nor the result of hero-worship. (Source)
Wirt also got confirmation from others who were there that day, like Thomas Jefferson, who agreed with the gist of Tucker's speech. William Safire says,
Judge Tucker recalled what he could and made up the rest. If that is so, Judge Tucker belongs among the ranks of history's best ghostwriters. (Source)
So there you have it. St. George Tucker might be the only political speechwriter to write a speech decades after it was given. Unless he had a Pensieve no one knows about, that speech is not exactly the same as the one Henry gave.