Libel

Libel is publishing something that is not true to ruin someone's reputation.

John Peter Zenger was arrested for libel because he printed bad things about Governor Cosby, but the things he printed were true.  That fact was used to get Peter out of court.

According to the American Heritage High School Dictionary: 

libel - n. 1a. A false publication in writing, print, signs or pictures that damages a person's reputation. b. The act of presenting such material to the public.