The killing of two New York policemen and protests against the use of excessive force by authorities have raised questions about whether individuals can be prosecuted for violent speech directed at police on social media and in public.
On Saturday a gunman, identified by authorities as Ismaaiyl Brinsley, ambushed two New York City police officers in Brooklyn while they were sitting in their patrol car.
Authorities said Brinsley's posts on Instagram, a mobile photo-sharing application, indicated he had been motivated by the deaths of unarmed black men Michael Brown and Eric Garner at the hands of white police officers.
Shortly before the shootings, Brinsley wrote "I'm putting wings on pigs today."
Compared with other countries, the United States has a strong guarantee of speech rights even when the speech displays racism, hatred or violence.
State laws, however, generally make it a crime to communicate a specific threat against a police officer or anyone else.
Generally, a threat "has to have some degree of specificity of who is going to be attacked, or what place is going to be attacked, or some other detail along those lines," said Eugene Volokh, a UCLA law professor.
Context matters in threat cases. So much so that in 2003, the US Supreme Court ruled that burning a cross was protected speech if done in an open field and not intended to intimidate someone specific, but potentially a crime if done before the home of an African American family.
The high court on December 1 revisited the law of threats to consider another question: Must prosecutors show that a person intended to threaten, or is it enough to show merely that a reasonable person would have felt threatened?
States are not uniform on that standard, and a ruling in the case is expected by the end of June.