After Anthony Elonis’s wife left him, he began to write graphically violent rap lyrics and post them to his Facebook account. In several posts, he fantasized about murdering his estranged wife. Others contained violent thoughts about the workplace from which he had been fired, his former co-workers, and an FBI agent who had investigated the matter. In one post, he even talked about massacring a local kindergarten class.
The decision:
Intent to threaten must be a demonstrated in order to convict for the criminal offense of "transmission of threats in interstate commerce". The court did not rule on whether or not "recklessness" would be sufficient.
http://www.oyez.org/cases/2010-2019/2014/2014_13_983 [oyez.org]
http://blogs.kentlaw.iit.edu/iscotus/elonis-v-united-states-treading-carefully-with-regard-to-threats-and-free-speech/ [iit.edu]
https://supreme.justia.com/cases/federal/us/575/13-983/opinion3.html [justia.com]