Fifth Amendment
n
1. an amendment to the US Constitution stating that no person may be compelled to testify against himself and that no person may be tried for a second time on a charge for which he has already been acquitted
(Law)
How so?
Several USSC rulings....these are just off the top of my head:
Albertson v. Subversive Activities Control Board
I could find more...but I'm at work.