DRY TORTUGAS — Fifteen descendants of Dr. Samuel Mudd plan another plea to clear his name, this time from the island garrison where Mudd was imprisoned for treating President Abraham Lincoln’s assassin.

Mudd spent nearly four years at Fort Jefferson, a six-sided red brick fort 70 miles west of Key West.

His grandson, Dr. Richard Mudd, 86, plans to lead an entourage of Mudds to the fort, now a national monument, on Friday.

“Our main objective is to inspect the prison site of my grandfather and sit in his prison cell and feel sorry for him,” said Mudd, a physician in Saginaw, Mich. “I think he was very badly treated by the government.”

Dr. Samuel Alexander Mudd was convicted of complicity in Lincoln’s assassination for setting the leg John Wilkes Booth broke in his leap to the stage of Ford’s Theater.

There was no proof Mudd knew the identity of his patient, who wore false whiskers and used the name Tyler when he came to Mudd’s Maryland farmhouse for treatment.

Mudd was shackled in irons and forced to wash sections of the fort every day. He was freed in 1869 and won a pardon from President Andrew Johnson after garrison officers petitioned for his release because he treated islanders during a yellow fever epidemic.

“He pardoned him, but the pardon only means that he leaves prison and has the right to vote. It had nothing to do with (the) question of innocence,” Mudd said Monday.

He has tried unsuccessfully since 1918 to clear his grandfather’s name, arguing that since it was a presidential commission that convicted Dr. Mudd, the president of the United States has the power to declare Mudd innocent.